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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                           July 29, 2013
Expires: January 30, 2014


                       JSON Web Algorithms (JWA)
                 draft-ietf-jose-json-web-algorithms-14

Abstract

   The JSON Web Algorithms (JWA) specification enumerates cryptographic
   algorithms and identifiers to be used with the JSON Web Signature
   (JWS), JSON Web Encryption (JWE), and JSON Web Key (JWK)
   specifications.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 30, 2014.

Copyright Notice

   Copyright (c) 2013 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
     1.1.  Notational Conventions . . . . . . . . . . . . . . . . . .  5
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Terms Incorporated from the JWS Specification  . . . . . .  5
     2.2.  Terms Incorporated from the JWE Specification  . . . . . .  6
     2.3.  Terms Incorporated from the JWK Specification  . . . . . .  9
     2.4.  Defined Terms  . . . . . . . . . . . . . . . . . . . . . .  9
   3.  Cryptographic Algorithms for JWS . . . . . . . . . . . . . . .  9
     3.1.  "alg" (Algorithm) Header Parameter Values for JWS  . . . .  9
     3.2.  MAC with HMAC SHA-2 Functions  . . . . . . . . . . . . . . 11
     3.3.  Digital Signature with RSASSA-PKCS1-V1_5 . . . . . . . . . 12
     3.4.  Digital Signature with ECDSA . . . . . . . . . . . . . . . 13
     3.5.  Digital Signature with RSASSA-PSS  . . . . . . . . . . . . 14
     3.6.  Using the Algorithm "none" . . . . . . . . . . . . . . . . 15
     3.7.  Additional Digital Signature/MAC Algorithms and
           Parameters . . . . . . . . . . . . . . . . . . . . . . . . 15
   4.  Cryptographic Algorithms for JWE . . . . . . . . . . . . . . . 16
     4.1.  "alg" (Algorithm) Header Parameter Values for JWE  . . . . 16
     4.2.  "enc" (Encryption Method) Header Parameter Values for
           JWE  . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     4.3.  Key Encryption with RSAES-PKCS1-V1_5 . . . . . . . . . . . 22
     4.4.  Key Encryption with RSAES OAEP . . . . . . . . . . . . . . 22
     4.5.  Key Wrapping with AES Key Wrap . . . . . . . . . . . . . . 22
     4.6.  Direct Encryption with a Shared Symmetric Key  . . . . . . 22
     4.7.  Key Agreement with Elliptic Curve Diffie-Hellman
           Ephemeral Static (ECDH-ES) . . . . . . . . . . . . . . . . 22
       4.7.1.  Header Parameters Used for ECDH Key Agreement  . . . . 23
         4.7.1.1.  "epk" (Ephemeral Public Key) Header Parameter  . . 23
         4.7.1.2.  "apu" (Agreement PartyUInfo) Header Parameter  . . 23
         4.7.1.3.  "apv" (Agreement PartyVInfo) Header Parameter  . . 24
       4.7.2.  Key Derivation for ECDH Key Agreement  . . . . . . . . 24
     4.8.  Key Encryption with AES GCM  . . . . . . . . . . . . . . . 25
       4.8.1.  Header Parameters Used for AES GCM Key Encryption  . . 26
         4.8.1.1.  "iv" (Initialization Vector) Header Parameter  . . 26
         4.8.1.2.  "tag" (Authentication Tag) Header Parameter  . . . 26
     4.9.  Key Encryption with PBES2  . . . . . . . . . . . . . . . . 26
       4.9.1.  Header Parameters Used for PBES2 Key Encryption  . . . 26
         4.9.1.1.  "p2s" (PBES2 salt) Parameter . . . . . . . . . . . 26
         4.9.1.2.  "p2c" (PBES2 count) Parameter  . . . . . . . . . . 27
     4.10. AES_CBC_HMAC_SHA2 Algorithms . . . . . . . . . . . . . . . 27
       4.10.1. Conventions Used in Defining AES_CBC_HMAC_SHA2 . . . . 27
       4.10.2. Generic AES_CBC_HMAC_SHA2 Algorithm  . . . . . . . . . 28
         4.10.2.1. AES_CBC_HMAC_SHA2 Encryption . . . . . . . . . . . 28
         4.10.2.2. AES_CBC_HMAC_SHA2 Decryption . . . . . . . . . . . 30
       4.10.3. AES_128_CBC_HMAC_SHA_256 . . . . . . . . . . . . . . . 30
       4.10.4. AES_192_CBC_HMAC_SHA_384 . . . . . . . . . . . . . . . 31



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       4.10.5. AES_256_CBC_HMAC_SHA_512 . . . . . . . . . . . . . . . 31
       4.10.6. Plaintext Encryption with AES_CBC_HMAC_SHA2  . . . . . 31
     4.11. Plaintext Encryption with AES GCM  . . . . . . . . . . . . 32
     4.12. Additional Encryption Algorithms and Parameters  . . . . . 32
   5.  Cryptographic Algorithms for JWK . . . . . . . . . . . . . . . 33
     5.1.  "kty" (Key Type) Parameter Values for JWK  . . . . . . . . 33
     5.2.  JWK Parameters for Elliptic Curve Keys . . . . . . . . . . 33
       5.2.1.  JWK Parameters for Elliptic Curve Public Keys  . . . . 33
         5.2.1.1.  "crv" (Curve) Parameter  . . . . . . . . . . . . . 34
         5.2.1.2.  "x" (X Coordinate) Parameter . . . . . . . . . . . 34
         5.2.1.3.  "y" (Y Coordinate) Parameter . . . . . . . . . . . 34
       5.2.2.  JWK Parameters for Elliptic Curve Private Keys . . . . 34
         5.2.2.1.  "d" (ECC Private Key) Parameter  . . . . . . . . . 34
     5.3.  JWK Parameters for RSA Keys  . . . . . . . . . . . . . . . 35
       5.3.1.  JWK Parameters for RSA Public Keys . . . . . . . . . . 35
         5.3.1.1.  "n" (Modulus) Parameter  . . . . . . . . . . . . . 35
         5.3.1.2.  "e" (Exponent) Parameter . . . . . . . . . . . . . 35
       5.3.2.  JWK Parameters for RSA Private Keys  . . . . . . . . . 35
         5.3.2.1.  "d" (Private Exponent) Parameter . . . . . . . . . 35
         5.3.2.2.  "p" (First Prime Factor) Parameter . . . . . . . . 36
         5.3.2.3.  "q" (Second Prime Factor) Parameter  . . . . . . . 36
         5.3.2.4.  "dp" (First Factor CRT Exponent) Parameter . . . . 36
         5.3.2.5.  "dq" (Second Factor CRT Exponent) Parameter  . . . 36
         5.3.2.6.  "qi" (First CRT Coefficient) Parameter . . . . . . 36
         5.3.2.7.  "oth" (Other Primes Info) Parameter  . . . . . . . 36
       5.3.3.  JWK Parameters for Symmetric Keys  . . . . . . . . . . 37
         5.3.3.1.  "k" (Key Value) Parameter  . . . . . . . . . . . . 37
     5.4.  Additional Key Types and Parameters  . . . . . . . . . . . 37
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 38
     6.1.  JSON Web Signature and Encryption Algorithms Registry  . . 38
       6.1.1.  Template . . . . . . . . . . . . . . . . . . . . . . . 38
       6.1.2.  Initial Registry Contents  . . . . . . . . . . . . . . 39
     6.2.  JSON Web Key Types Registry  . . . . . . . . . . . . . . . 44
       6.2.1.  Registration Template  . . . . . . . . . . . . . . . . 44
       6.2.2.  Initial Registry Contents  . . . . . . . . . . . . . . 45
     6.3.  JSON Web Key Parameters Registration . . . . . . . . . . . 45
       6.3.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 45
     6.4.  Registration of JWE Header Parameter Names . . . . . . . . 47
       6.4.1.  Registry Contents  . . . . . . . . . . . . . . . . . . 47
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 48
     7.1.  Reusing Key Material when Encrypting Keys  . . . . . . . . 49
     7.2.  Password Considerations  . . . . . . . . . . . . . . . . . 49
   8.  Internationalization Considerations  . . . . . . . . . . . . . 50
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 50
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 50
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 52
   Appendix A.  Digital Signature/MAC Algorithm Identifier
                Cross-Reference . . . . . . . . . . . . . . . . . . . 53



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   Appendix B.  Encryption Algorithm Identifier Cross-Reference . . . 56
   Appendix C.  Test Cases for AES_CBC_HMAC_SHA2 Algorithms . . . . . 59
     C.1.  Test Cases for AES_128_CBC_HMAC_SHA_256  . . . . . . . . . 60
     C.2.  Test Cases for AES_192_CBC_HMAC_SHA_384  . . . . . . . . . 61
     C.3.  Test Cases for AES_256_CBC_HMAC_SHA_512  . . . . . . . . . 62
   Appendix D.  Example ECDH-ES Key Agreement Computation . . . . . . 63
   Appendix E.  Acknowledgements  . . . . . . . . . . . . . . . . . . 65
   Appendix F.  Document History  . . . . . . . . . . . . . . . . . . 65
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 72










































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1.  Introduction

   The JSON Web Algorithms (JWA) specification enumerates cryptographic
   algorithms and identifiers to be used with the JSON Web Signature
   (JWS) [JWS], JSON Web Encryption (JWE) [JWE], and JSON Web Key (JWK)
   [JWK] specifications.  All these specifications utilize JavaScript
   Object Notation (JSON) [RFC4627] based data structures.  This
   specification also describes the semantics and operations that are
   specific to these algorithms and key types.

   Enumerating the algorithms and identifiers for them in this
   specification, rather than in the JWS, JWE, and JWK specifications,
   is intended to allow them to remain unchanged in the face of changes
   in the set of required, recommended, optional, and deprecated
   algorithms over time.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in Key words for use in
   RFCs to Indicate Requirement Levels [RFC2119].


2.  Terminology

2.1.  Terms Incorporated from the JWS Specification

   These terms defined by the JSON Web Signature (JWS) [JWS]
   specification are incorporated into this specification:

   JSON Web Signature (JWS)  A data structure representing a digitally
      signed or MACed message.  The structure represents three values:
      the JWS Header, the JWS Payload, and the JWS Signature.

   JSON Text Object  A UTF-8 [RFC3629] encoded text string representing
      a JSON object; the syntax of JSON objects is defined in Section
      2.2 of [RFC4627].

   JWS Header  A JSON Text Object (or JSON Text Objects, when using the
      JWS JSON Serialization) that describes the digital signature or
      MAC operation applied to create the JWS Signature value.  The
      members of the JWS Header object(s) are Header Parameters.

   JWS Payload  The sequence of octets to be secured -- a.k.a., the
      message.  The payload can contain an arbitrary sequence of octets.





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   JWS Signature  A sequence of octets containing the cryptographic
      material that ensures the integrity of the JWS Protected Header
      and the JWS Payload.  The JWS Signature value is a digital
      signature or MAC value calculated over the JWS Signing Input using
      the parameters specified in the JWS Header.

   JWS Protected Header  A JSON Text Object that contains the portion of
      the JWS Header that is integrity protected.  For the JWS Compact
      Serialization, this comprises the entire JWS Header.  For the JWS
      JSON Serialization, this is one component of the JWS Header.

   Base64url Encoding  The URL- and filename-safe Base64 encoding
      described in RFC 4648 [RFC4648], Section 5, with the (non URL-
      safe) '=' padding characters omitted, as permitted by Section 3.2.
      (See Appendix C of [JWS] for notes on implementing base64url
      encoding without padding.)

   Encoded JWS Header  Base64url encoding of the JWS Protected Header.

   Encoded JWS Payload  Base64url encoding of the JWS Payload.

   Encoded JWS Signature  Base64url encoding of the JWS Signature.

   JWS Signing Input  The concatenation of the Encoded JWS Header, a
      period ('.') character, and the Encoded JWS Payload.

   Collision Resistant Namespace  A namespace that allows names to be
      allocated in a manner such that they are highly unlikely to
      collide with other names.  For instance, collision resistance can
      be achieved through administrative delegation of portions of the
      namespace or through use of collision-resistant name allocation
      functions.  Examples of Collision Resistant Namespaces include:
      Domain Names, Object Identifiers (OIDs) as defined in the ITU-T
      X.660 and X.670 Recommendation series, and Universally Unique
      IDentifiers (UUIDs) [RFC4122].  When using an administratively
      delegated namespace, the definer of a name needs to take
      reasonable precautions to ensure they are in control of the
      portion of the namespace they use to define the name.

2.2.  Terms Incorporated from the JWE Specification

   These terms defined by the JSON Web Encryption (JWE) [JWE]
   specification are incorporated into this specification:








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   JSON Web Encryption (JWE)  A data structure representing an encrypted
      message.  The structure represents five values: the JWE Header,
      the JWE Encrypted Key, the JWE Initialization Vector, the JWE
      Ciphertext, and the JWE Authentication Tag.

   Authenticated Encryption  An Authenticated Encryption algorithm is
      one that provides an integrated content integrity check.
      Authenticated Encryption algorithms accept two inputs, the
      Plaintext and the Additional Authenticated Data value, and produce
      two outputs, the Ciphertext and the Authentication Tag value.  AES
      Galois/Counter Mode (GCM) is one such algorithm.

   Plaintext  The sequence of octets to be encrypted -- a.k.a., the
      message.  The plaintext can contain an arbitrary sequence of
      octets.

   Ciphertext  An encrypted representation of the Plaintext.

   Additional Authenticated Data (AAD)  An input to an Authenticated
      Encryption operation that is integrity protected but not
      encrypted.

   Authentication Tag  An output of an Authenticated Encryption
      operation that ensures the integrity of the Ciphertext and the
      Additional Authenticated Data.  Note that some algorithms may not
      use an Authentication Tag, in which case this value is the empty
      octet sequence.

   Content Encryption Key (CEK)  A symmetric key for the Authenticated
      Encryption algorithm used to encrypt the Plaintext for the
      recipient to produce the Ciphertext and the Authentication Tag.

   JWE Header  A JSON Text Object (or JSON Text Objects, when using the
      JWE JSON Serialization) that describes the encryption operations
      applied to create the JWE Encrypted Key, the JWE Ciphertext, and
      the JWE Authentication Tag. The members of the JWE Header
      object(s) are Header Parameters.

   JWE Encrypted Key  The result of encrypting the Content Encryption
      Key (CEK) with the intended recipient's key using the specified
      algorithm.  Note that for some algorithms, the JWE Encrypted Key
      value is specified as being the empty octet sequence.

   JWE Initialization Vector  A sequence of octets containing the
      Initialization Vector used when encrypting the Plaintext.  Note
      that some algorithms may not use an Initialization Vector, in
      which case this value is the empty octet sequence.




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   JWE Ciphertext  A sequence of octets containing the Ciphertext for a
      JWE.

   JWE Authentication Tag  A sequence of octets containing the
      Authentication Tag for a JWE.

   JWE Protected Header  A JSON Text Object that contains the portion of
      the JWE Header that is integrity protected.  For the JWE Compact
      Serialization, this comprises the entire JWE Header.  For the JWE
      JSON Serialization, this is one component of the JWE Header.

   Encoded JWE Header  Base64url encoding of the JWE Protected Header.

   Encoded JWE Encrypted Key  Base64url encoding of the JWE Encrypted
      Key.

   Encoded JWE Initialization Vector  Base64url encoding of the JWE
      Initialization Vector.

   Encoded JWE Ciphertext  Base64url encoding of the JWE Ciphertext.

   Encoded JWE Authentication Tag  Base64url encoding of the JWE
      Authentication Tag.

   Key Management Mode  A method of determining the Content Encryption
      Key (CEK) value to use.  Each algorithm used for determining the
      CEK value uses a specific Key Management Mode.  Key Management
      Modes employed by this specification are Key Encryption, Key
      Wrapping, Direct Key Agreement, Key Agreement with Key Wrapping,
      and Direct Encryption.

   Key Encryption  A Key Management Mode in which the Content Encryption
      Key (CEK) value is encrypted to the intended recipient using an
      asymmetric encryption algorithm.

   Key Wrapping  A Key Management Mode in which the Content Encryption
      Key (CEK) value is encrypted to the intended recipient using a
      symmetric key wrapping algorithm.

   Direct Key Agreement  A Key Management Mode in which a key agreement
      algorithm is used to agree upon the Content Encryption Key (CEK)
      value.

   Key Agreement with Key Wrapping  A Key Management Mode in which a key
      agreement algorithm is used to agree upon a symmetric key used to
      encrypt the Content Encryption Key (CEK) value to the intended
      recipient using a symmetric key wrapping algorithm.




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   Direct Encryption  A Key Management Mode in which the Content
      Encryption Key (CEK) value used is the secret symmetric key value
      shared between the parties.

2.3.  Terms Incorporated from the JWK Specification

   These terms defined by the JSON Web Key (JWK) [JWK] specification are
   incorporated into this specification:

   JSON Web Key (JWK)  A JSON object that represents a cryptographic
      key.

   JSON Web Key Set (JWK Set)  A JSON object that contains an array of
      JWKs as the value of its "keys" member.

2.4.  Defined Terms

   These terms are defined for use by this specification:

   Header Parameter  A name/value pair that is member of a JWS Header or
      JWE Header.

   Header Parameter Name  The name of a member of a JSON object
      representing a JWS Header or JWE Header.

   Header Parameter Value  The value of a member of a JSON object
      representing a JWS Header or JWE Header.


3.  Cryptographic Algorithms for JWS

   JWS uses cryptographic algorithms to digitally sign or create a
   Message Authentication Codes (MAC) of the contents of the JWS Header
   and the JWS Payload.  The use of the following algorithms for
   producing JWSs is defined in this section.

3.1.  "alg" (Algorithm) Header Parameter Values for JWS

   The table below is the set of "alg" (algorithm) header parameter
   values defined by this specification for use with JWS, each of which
   is explained in more detail in the following sections:










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   +-----------+--------------------------------------+----------------+
   | alg       | Digital Signature or MAC Algorithm   | Implementation |
   | Parameter |                                      | Requirements   |
   | Value     |                                      |                |
   +-----------+--------------------------------------+----------------+
   | HS256     | HMAC using SHA-256 hash algorithm    | REQUIRED       |
   | HS384     | HMAC using SHA-384 hash algorithm    | OPTIONAL       |
   | HS512     | HMAC using SHA-512 hash algorithm    | OPTIONAL       |
   | RS256     | RSASSA-PKCS-v1_5 using SHA-256 hash  | RECOMMENDED    |
   |           | algorithm                            |                |
   | RS384     | RSASSA-PKCS-v1_5 using SHA-384 hash  | OPTIONAL       |
   |           | algorithm                            |                |
   | RS512     | RSASSA-PKCS-v1_5 using SHA-512 hash  | OPTIONAL       |
   |           | algorithm                            |                |
   | ES256     | ECDSA using P-256 curve and SHA-256  | RECOMMENDED+   |
   |           | hash algorithm                       |                |
   | ES384     | ECDSA using P-384 curve and SHA-384  | OPTIONAL       |
   |           | hash algorithm                       |                |
   | ES512     | ECDSA using P-521 curve and SHA-512  | OPTIONAL       |
   |           | hash algorithm                       |                |
   | PS256     | RSASSA-PSS using SHA-256 hash        | OPTIONAL       |
   |           | algorithm and MGF1 mask generation   |                |
   |           | function with SHA-256                |                |
   | PS384     | RSASSA-PSS using SHA-384 hash        | OPTIONAL       |
   |           | algorithm and MGF1 mask generation   |                |
   |           | function with SHA-384                |                |
   | PS512     | RSASSA-PSS using SHA-512 hash        | OPTIONAL       |
   |           | algorithm and MGF1 mask generation   |                |
   |           | function with SHA-512                |                |
   | none      | No digital signature or MAC value    | REQUIRED       |
   |           | included                             |                |
   +-----------+--------------------------------------+----------------+

   All the names are short because a core goal of JWS is for the
   representations to be compact.  However, there is no a priori length
   restriction on "alg" values.

   The use of "+" in the Implementation Requirements indicates that the
   requirement strength is likely to be increased in a future version of
   the specification.

   See Appendix A for a table cross-referencing the digital signature
   and MAC "alg" (algorithm) values used in this specification with the
   equivalent identifiers used by other standards and software packages.







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3.2.  MAC with HMAC SHA-2 Functions

   Hash-based Message Authentication Codes (HMACs) enable one to use a
   secret plus a cryptographic hash function to generate a Message
   Authentication Code (MAC).  This can be used to demonstrate that the
   MAC matches the hashed content, in this case the JWS Signing Input,
   which therefore demonstrates that whoever generated the MAC was in
   possession of the secret.  The means of exchanging the shared key is
   outside the scope of this specification.

   The algorithm for implementing and validating HMACs is provided in
   RFC 2104 [RFC2104].  This section defines the use of the HMAC SHA-
   256, HMAC SHA-384, and HMAC SHA-512 functions [SHS].  The "alg"
   (algorithm) header parameter values "HS256", "HS384", and "HS512" are
   used in the JWS Header to indicate that the Encoded JWS Signature
   contains a base64url encoded HMAC value using the respective hash
   function.

   A key of the same size as the hash output (for instance, 256 bits for
   "HS256") or larger MUST be used with this algorithm.

   The HMAC SHA-256 MAC is generated per RFC 2104, using SHA-256 as the
   hash algorithm "H", using the octets of the ASCII [USASCII]
   representation of the JWS Signing Input as the "text" value, and
   using the shared key.  The HMAC output value is the JWS Signature.
   The JWS signature is base64url encoded to produce the Encoded JWS
   Signature.

   The HMAC SHA-256 MAC for a JWS is validated by computing an HMAC
   value per RFC 2104, using SHA-256 as the hash algorithm "H", using
   the octets of the ASCII representation of the received JWS Signing
   Input as the "text" value, and using the shared key.  This computed
   HMAC value is then compared to the result of base64url decoding the
   received Encoded JWS signature.  Alternatively, the computed HMAC
   value can be base64url encoded and compared to the received Encoded
   JWS Signature, as this comparison produces the same result as
   comparing the unencoded values.  In either case, if the values match,
   the HMAC has been validated.  If the validation fails, the JWS MUST
   be rejected.

   Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is
   performed identically to the procedure for HMAC SHA-256 - just using
   the corresponding hash algorithm with correspondingly larger minimum
   key sizes and result values: 384 bits each for HMAC SHA-384 and 512
   bits each for HMAC SHA-512.

   An example using this algorithm is shown in Appendix A.1 of [JWS].




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3.3.  Digital Signature with RSASSA-PKCS1-V1_5

   This section defines the use of the RSASSA-PKCS1-V1_5 digital
   signature algorithm as defined in Section 8.2 of RFC 3447 [RFC3447]
   (commonly known as PKCS #1), using SHA-256, SHA-384, or SHA-512 [SHS]
   as the hash functions.  The "alg" (algorithm) header parameter values
   "RS256", "RS384", and "RS512" are used in the JWS Header to indicate
   that the Encoded JWS Signature contains a base64url encoded RSASSA-
   PKCS1-V1_5 digital signature using the respective hash function.

   A key of size 2048 bits or larger MUST be used with these algorithms.

   The RSASSA-PKCS1-V1_5 SHA-256 digital signature is generated as
   follows:

   1.  Generate a digital signature of the octets of the ASCII
       representation of the JWS Signing Input using RSASSA-PKCS1-V1_5-
       SIGN and the SHA-256 hash function with the desired private key.
       The output will be an octet sequence.

   2.  Base64url encode the resulting octet sequence.

   The output is the Encoded JWS Signature for that JWS.

   The RSASSA-PKCS1-V1_5 SHA-256 digital signature for a JWS is
   validated as follows:

   1.  Take the Encoded JWS Signature and base64url decode it into an
       octet sequence.  If decoding fails, the JWS MUST be rejected.

   2.  Submit the octets of the ASCII representation of the JWS Signing
       Input and the public key corresponding to the private key used by
       the signer to the RSASSA-PKCS1-V1_5-VERIFY algorithm using SHA-
       256 as the hash function.

   3.  If the validation fails, the JWS MUST be rejected.

   Signing with the RSASSA-PKCS1-V1_5 SHA-384 and RSASSA-PKCS1-V1_5 SHA-
   512 algorithms is performed identically to the procedure for RSASSA-
   PKCS1-V1_5 SHA-256 - just using the corresponding hash algorithm with
   correspondingly larger result values: 384 bits for RSASSA-PKCS1-V1_5
   SHA-384 and 512 bits for RSASSA-PKCS1-V1_5 SHA-512.

   An example using this algorithm is shown in Appendix A.2 of [JWS].







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3.4.  Digital Signature with ECDSA

   The Elliptic Curve Digital Signature Algorithm (ECDSA) [DSS] provides
   for the use of Elliptic Curve cryptography, which is able to provide
   equivalent security to RSA cryptography but using shorter key sizes
   and with greater processing speed.  This means that ECDSA digital
   signatures will be substantially smaller in terms of length than
   equivalently strong RSA digital signatures.

   This specification defines the use of ECDSA with the P-256 curve and
   the SHA-256 cryptographic hash function, ECDSA with the P-384 curve
   and the SHA-384 hash function, and ECDSA with the P-521 curve and the
   SHA-512 hash function.  The P-256, P-384, and P-521 curves are
   defined in [DSS].  The "alg" (algorithm) header parameter values
   "ES256", "ES384", and "ES512" are used in the JWS Header to indicate
   that the Encoded JWS Signature contains a base64url encoded ECDSA
   P-256 SHA-256, ECDSA P-384 SHA-384, or ECDSA P-521 SHA-512 digital
   signature, respectively.

   The ECDSA P-256 SHA-256 digital signature is generated as follows:

   1.  Generate a digital signature of the octets of the ASCII
       representation of the JWS Signing Input using ECDSA P-256 SHA-256
       with the desired private key.  The output will be the pair (R,
       S), where R and S are 256 bit unsigned integers.

   2.  Turn R and S into octet sequences in big endian order, with each
       array being be 32 octets long.  The array representations MUST
       NOT be shortened to omit any leading zero octets contained in the
       values.

   3.  Concatenate the two octet sequences in the order R and then S.
       (Note that many ECDSA implementations will directly produce this
       concatenation as their output.)

   4.  Base64url encode the resulting 64 octet sequence.

   The output is the Encoded JWS Signature for the JWS.

   The ECDSA P-256 SHA-256 digital signature for a JWS is validated as
   follows:

   1.  Take the Encoded JWS Signature and base64url decode it into an
       octet sequence.  If decoding fails, the JWS MUST be rejected.

   2.  The output of the base64url decoding MUST be a 64 octet sequence.
       If decoding does not result in a 64 octet sequence, the JWS MUST
       be rejected.



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   3.  Split the 64 octet sequence into two 32 octet sequences.  The
       first array will be R and the second S (with both being in big
       endian octet order).

   4.  Submit the octets of the ASCII representation of the JWS Signing
       Input R, S and the public key (x, y) to the ECDSA P-256 SHA-256
       validator.

   5.  If the validation fails, the JWS MUST be rejected.

   Note that ECDSA digital signature contains a value referred to as K,
   which is a random number generated for each digital signature
   instance.  This means that two ECDSA digital signatures using exactly
   the same input parameters will output different signature values
   because their K values will be different.  A consequence of this is
   that one cannot validate an ECDSA signature by recomputing the
   signature and comparing the results.

   Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512
   algorithms is performed identically to the procedure for ECDSA P-256
   SHA-256 - just using the corresponding hash algorithm with
   correspondingly larger result values.  For ECDSA P-384 SHA-384, R and
   S will be 384 bits each, resulting in a 96 octet sequence.  For ECDSA
   P-521 SHA-512, R and S will be 521 bits each, resulting in a 132
   octet sequence.

   Examples using these algorithms are shown in Appendices A.3 and A.4
   of [JWS].

3.5.  Digital Signature with RSASSA-PSS

   This section defines the use of the RSASSA-PSS digital signature
   algorithm as defined in Section 8.1 of RFC 3447 [RFC3447] with the
   MGF1 mask generation function, always using the same hash function
   for both the RSASSA-PSS hash function and the MGF1 hash function.
   Use of SHA-256, SHA-384, and SHA-512 as these hash functions is
   defined.  All other algorithm parameters use the defaults specified
   in Section A.2.3 of RFC 3447.  The "alg" (algorithm) header parameter
   values "PS256", "PS384", and "PS512" are used in the JWS Header to
   indicate that the Encoded JWS Signature contains a base64url encoded
   RSASSA-PSS digital signature using the respective hash function in
   both roles.

   A key of size 2048 bits or larger MUST be used with this algorithm.

   The RSASSA-PSS SHA-256 digital signature is generated as follows:





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   1.  Generate a digital signature of the octets of the ASCII
       representation of the JWS Signing Input using RSASSA-PSS-SIGN,
       the SHA-256 hash function, and the MGF1 mask generation function
       with SHA-256 with the desired private key.  The output will be an
       octet sequence.

   2.  Base64url encode the resulting octet sequence.

   The output is the Encoded JWS Signature for that JWS.

   The RSASSA-PSS SHA-256 digital signature for a JWS is validated as
   follows:

   1.  Take the Encoded JWS Signature and base64url decode it into an
       octet sequence.  If decoding fails, the JWS MUST be rejected.

   2.  Submit the octets of the ASCII representation of the JWS Signing
       Input and the public key corresponding to the private key used by
       the signer to the RSASSA-PSS-VERIFY algorithm using SHA-256 as
       the hash function and using MGF1 as the mask generation function
       with SHA-256.

   3.  If the validation fails, the JWS MUST be rejected.

   Signing with the RSASSA-PSS SHA-384 and RSASSA-PSS SHA-512 algorithms
   is performed identically to the procedure for RSASSA-PSS SHA-256 -
   just using the alternative hash algorithm in both roles.

3.6.  Using the Algorithm "none"

   JWSs MAY also be created that do not provide integrity protection.
   Such a JWS is called a "Plaintext JWS".  Plaintext JWSs MUST use the
   "alg" value "none", and are formatted identically to other JWSs, but
   with the empty string for its JWS Signature value.

3.7.  Additional Digital Signature/MAC Algorithms and Parameters

   Additional algorithms MAY be used to protect JWSs with corresponding
   "alg" (algorithm) header parameter values being defined to refer to
   them.  New "alg" header parameter values SHOULD either be registered
   in the IANA JSON Web Signature and Encryption Algorithms registry
   Section 6.1 or be a value that contains a Collision Resistant
   Namespace.  In particular, it is permissible to use the algorithm
   identifiers defined in XML DSIG [RFC3275], XML DSIG 2.0
   [W3C.CR-xmldsig-core2-20120124], and related specifications as "alg"
   values.

   As indicated by the common registry, JWSs and JWEs share a common



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   "alg" value space.  The values used by the two specifications MUST be
   distinct, as the "alg" value can be used to determine whether the
   object is a JWS or JWE.

   Likewise, additional reserved Header Parameter Names can be defined
   via the IANA JSON Web Signature and Encryption Header Parameters
   registry [JWS].  As indicated by the common registry, JWSs and JWEs
   share a common header parameter space; when a parameter is used by
   both specifications, its usage must be compatible between the
   specifications.


4.  Cryptographic Algorithms for JWE

   JWE uses cryptographic algorithms to encrypt the Content Encryption
   Key (CEK) and the Plaintext.  This section specifies a set of
   specific algorithms for these purposes.

4.1.  "alg" (Algorithm) Header Parameter Values for JWE

   The table below is the set of "alg" (algorithm) header parameter
   values that are defined by this specification for use with JWE.
   These algorithms are used to encrypt the CEK, producing the JWE
   Encrypted Key, or to use key agreement to agree upon the CEK.

   +-------------------+-----------------+------------+----------------+
   | alg Parameter     | Key Management  | Additional | Implementation |
   | Value             | Algorithm       | Header     | Requirements   |
   |                   |                 | Parameters |                |
   +-------------------+-----------------+------------+----------------+
   | RSA1_5            | RSAES-PKCS1-V1_ | (none)     | REQUIRED       |
   |                   | 5[RFC3447]      |            |                |
   | RSA-OAEP          | RSAES using     | (none)     | OPTIONAL       |
   |                   | Optimal         |            |                |
   |                   | Asymmetric      |            |                |
   |                   | Encryption      |            |                |
   |                   | Padding (OAEP)  |            |                |
   |                   | [RFC3447], with |            |                |
   |                   | the default     |            |                |
   |                   | parameters      |            |                |
   |                   | specified by    |            |                |
   |                   | RFC 3447 in     |            |                |
   |                   | Section A.2.1   |            |                |








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   | A128KW            | Advanced        | (none)     | RECOMMENDED    |
   |                   | Encryption      |            |                |
   |                   | Standard (AES)  |            |                |
   |                   | Key Wrap        |            |                |
   |                   | Algorithm       |            |                |
   |                   | [RFC3394] using |            |                |
   |                   | the default     |            |                |
   |                   | initial value   |            |                |
   |                   | specified in    |            |                |
   |                   | Section 2.2.3.1 |            |                |
   |                   | and using 128   |            |                |
   |                   | bit keys        |            |                |
   | A192KW            | AES Key Wrap    | (none)     | OPTIONAL       |
   |                   | Algorithm using |            |                |
   |                   | the default     |            |                |
   |                   | initial value   |            |                |
   |                   | specified in    |            |                |
   |                   | Section 2.2.3.1 |            |                |
   |                   | and using 192   |            |                |
   |                   | bit keys        |            |                |
   | A256KW            | AES Key Wrap    | (none)     | RECOMMENDED    |
   |                   | Algorithm using |            |                |
   |                   | the default     |            |                |
   |                   | initial value   |            |                |
   |                   | specified in    |            |                |
   |                   | Section 2.2.3.1 |            |                |
   |                   | and using 256   |            |                |
   |                   | bit keys        |            |                |
   | dir               | Direct use of a | (none)     | RECOMMENDED    |
   |                   | shared          |            |                |
   |                   | symmetric key   |            |                |
   |                   | as the Content  |            |                |
   |                   | Encryption Key  |            |                |
   |                   | (CEK) for the   |            |                |
   |                   | content         |            |                |
   |                   | encryption step |            |                |
   |                   | (rather than    |            |                |
   |                   | using the       |            |                |
   |                   | symmetric key   |            |                |
   |                   | to wrap the     |            |                |
   |                   | CEK)            |            |                |










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   | ECDH-ES           | Elliptic Curve  | "epk",     | RECOMMENDED+   |
   |                   | Diffie-Hellman  | "apu",     |                |
   |                   | Ephemeral       | "apv"      |                |
   |                   | Static          |            |                |
   |                   | [RFC6090] key   |            |                |
   |                   | agreement using |            |                |
   |                   | the Concat KDF, |            |                |
   |                   | as defined in   |            |                |
   |                   | Section 5.8.1   |            |                |
   |                   | of              |            |                |
   |                   | [NIST.800-56A], |            |                |
   |                   | with the        |            |                |
   |                   | agreed-upon key |            |                |
   |                   | being used      |            |                |
   |                   | directly as the |            |                |
   |                   | Content         |            |                |
   |                   | Encryption Key  |            |                |
   |                   | (CEK) (rather   |            |                |
   |                   | than being used |            |                |
   |                   | to wrap the     |            |                |
   |                   | CEK), as        |            |                |
   |                   | specified in    |            |                |
   |                   | Section 4.7     |            |                |
   | ECDH-ES+A128KW    | Elliptic Curve  | "epk",     | RECOMMENDED    |
   |                   | Diffie-Hellman  | "apu",     |                |
   |                   | Ephemeral       | "apv"      |                |
   |                   | Static key      |            |                |
   |                   | agreement per   |            |                |
   |                   | "ECDH-ES" and   |            |                |
   |                   | Section 4.7,    |            |                |
   |                   | where the       |            |                |
   |                   | agreed-upon key |            |                |
   |                   | is used to wrap |            |                |
   |                   | the Content     |            |                |
   |                   | Encryption Key  |            |                |
   |                   | (CEK) with the  |            |                |
   |                   | "A128KW"        |            |                |
   |                   | function        |            |                |
   |                   | (rather than    |            |                |
   |                   | being used      |            |                |
   |                   | directly as the |            |                |
   |                   | CEK)            |            |                |









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   | ECDH-ES+A192KW    | Elliptic Curve  | "epk",     | OPTIONAL       |
   |                   | Diffie-Hellman  | "apu",     |                |
   |                   | Ephemeral       | "apv"      |                |
   |                   | Static key      |            |                |
   |                   | agreement,      |            |                |
   |                   | where the       |            |                |
   |                   | agreed-upon key |            |                |
   |                   | is used to wrap |            |                |
   |                   | the Content     |            |                |
   |                   | Encryption Key  |            |                |
   |                   | (CEK) with the  |            |                |
   |                   | "A192KW"        |            |                |
   |                   | function        |            |                |
   |                   | (rather than    |            |                |
   |                   | being used      |            |                |
   |                   | directly as the |            |                |
   |                   | CEK)            |            |                |
   | ECDH-ES+A256KW    | Elliptic Curve  | "epk",     | RECOMMENDED    |
   |                   | Diffie-Hellman  | "apu",     |                |
   |                   | Ephemeral       | "apv"      |                |
   |                   | Static key      |            |                |
   |                   | agreement,      |            |                |
   |                   | where the       |            |                |
   |                   | agreed-upon key |            |                |
   |                   | is used to wrap |            |                |
   |                   | the Content     |            |                |
   |                   | Encryption Key  |            |                |
   |                   | (CEK) with the  |            |                |
   |                   | "A256KW"        |            |                |
   |                   | function        |            |                |
   |                   | (rather than    |            |                |
   |                   | being used      |            |                |
   |                   | directly as the |            |                |
   |                   | CEK)            |            |                |
   | A128GCMKW         | AES in          | "iv",      | OPTIONAL       |
   |                   | Galois/Counter  | "tag"      |                |
   |                   | Mode (GCM)      |            |                |
   |                   | [AES]           |            |                |
   |                   | [NIST.800-38D]  |            |                |
   |                   | using 128 bit   |            |                |
   |                   | keys            |            |                |
   | A192GCMKW         | AES GCM using   | "iv",      | OPTIONAL       |
   |                   | 192 bit keys    | "tag"      |                |
   | A256GCMKW         | AES GCM using   | "iv",      | OPTIONAL       |
   |                   | 256 bit keys    | "tag"      |                |






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   | PBES2-HS256+A128K | PBES2 [RFC2898] | "p2s",     | OPTIONAL       |
   | W                 | with HMAC       | "p2c"      |                |
   |                   | SHA-256 as the  |            |                |
   |                   | PRF and AES Key |            |                |
   |                   | Wrap [RFC3394]  |            |                |
   |                   | using 128 bit   |            |                |
   |                   | keys for the    |            |                |
   |                   | encryption      |            |                |
   |                   | scheme          |            |                |
   | PBES2-HS256+A192K | PBES2 with HMAC | "p2s",     | OPTIONAL       |
   | W                 | SHA-256 as the  | "p2c"      |                |
   |                   | PRF and AES Key |            |                |
   |                   | Wrap using 192  |            |                |
   |                   | bit keys for    |            |                |
   |                   | the encryption  |            |                |
   |                   | scheme          |            |                |
   | PBES2-HS256+A256K | PBES2 with HMAC | "p2s",     | OPTIONAL       |
   | W                 | SHA-256 as the  | "p2c"      |                |
   |                   | PRF and AES Key |            |                |
   |                   | Wrap using 256  |            |                |
   |                   | bit keys for    |            |                |
   |                   | the encryption  |            |                |
   |                   | scheme          |            |                |
   +-------------------+-----------------+------------+----------------+

   All the names are short because a core goal of JWE is for the
   representations to be compact.  However, there is no a priori length
   restriction on "alg" values.

   The Additional Header Parameters column indicates what additional
   Header Parameters are used by the algorithm, beyond "alg", which all
   use.  All but "dir" and "ECDH-ES" also produce a JWE Encrypted Key
   value.

   The use of "+" in the Implementation Requirements indicates that the
   requirement strength is likely to be increased in a future version of
   the specification.

4.2.  "enc" (Encryption Method) Header Parameter Values for JWE

   The table below is the set of "enc" (encryption method) header
   parameter values that are defined by this specification for use with
   JWE.  These algorithms are used to encrypt the Plaintext, which
   produces the Ciphertext.







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   +-------------+------------------------+------------+---------------+
   | enc         | Content Encryption     | Additional | Implementatio |
   | Parameter   | Algorithm              | Header     | nRequirements |
   | Value       |                        | Parameters |               |
   +-------------+------------------------+------------+---------------+
   | A128CBC-HS2 | The                    | (none)     | REQUIRED      |
   | 56          | AES_128_CBC_HMAC_SHA_2 |            |               |
   |             | 56 authenticated       |            |               |
   |             |  encryption algorithm, |            |               |
   |             |  as defined in         |            |               |
   |             |  Section 4.10.3.  This |            |               |
   |             |  algorithm uses a 256  |            |               |
   |             |  bit key.              |            |               |
   | A192CBC-HS3 | The                    | (none)     | OPTIONAL      |
   | 84          | AES_192_CBC_HMAC_SHA_3 |            |               |
   |             | 84 authenticated       |            |               |
   |             |  encryption algorithm, |            |               |
   |             |  as defined in         |            |               |
   |             |  Section 4.10.4.  This |            |               |
   |             |  algorithm uses a 384  |            |               |
   |             |  bit key.              |            |               |
   | A256CBC-HS5 | The                    | (none)     | REQUIRED      |
   | 12          | AES_256_CBC_HMAC_SHA_5 |            |               |
   |             | 12 authenticated       |            |               |
   |             |  encryption algorithm, |            |               |
   |             |  as defined in         |            |               |
   |             |  Section 4.10.5.  This |            |               |
   |             |  algorithm uses a 512  |            |               |
   |             |  bit key.              |            |               |
   | A128GCM     | AES in Galois/Counter  | (none)     | RECOMMENDED   |
   |             | Mode (GCM) [AES]       |            |               |
   |             | [NIST.800-38D] using   |            |               |
   |             | 128 bit keys           |            |               |
   | A192GCM     | AES GCM using 192 bit  | (none)     | OPTIONAL      |
   |             | keys                   |            |               |
   | A256GCM     | AES GCM using 256 bit  | (none)     | RECOMMENDED   |
   |             | keys                   |            |               |
   +-------------+------------------------+------------+---------------+

   The Additional Header Parameters column indicates what additional
   Header Parameters are used by the algorithm, beyond "enc", which all
   use.  All also use a JWE Initialization Vector value and produce JWE
   Ciphertext and JWE Authentication Tag values.

   See Appendix B for a table cross-referencing the encryption "alg"
   (algorithm) and "enc" (encryption method) values used in this
   specification with the equivalent identifiers used by other standards
   and software packages.



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4.3.  Key Encryption with RSAES-PKCS1-V1_5

   This section defines the specifics of encrypting a JWE CEK with
   RSAES-PKCS1-V1_5 [RFC3447].  The "alg" header parameter value
   "RSA1_5" is used in this case.

   A key of size 2048 bits or larger MUST be used with this algorithm.

   An example using this algorithm is shown in Appendix A.2 of [JWE].

4.4.  Key Encryption with RSAES OAEP

   This section defines the specifics of encrypting a JWE CEK with RSAES
   using Optimal Asymmetric Encryption Padding (OAEP) [RFC3447], with
   the default parameters specified by RFC 3447 in Section A.2.1.  The
   "alg" header parameter value "RSA-OAEP" is used in this case.

   A key of size 2048 bits or larger MUST be used with this algorithm.

   An example using this algorithm is shown in Appendix A.1 of [JWE].

4.5.  Key Wrapping with AES Key Wrap

   This section defines the specifics of encrypting a JWE CEK with the
   Advanced Encryption Standard (AES) Key Wrap Algorithm [RFC3394] using
   the default initial value specified in Section 2.2.3.1 using 128,
   192, or 256 bit keys.  The "alg" header parameter values "A128KW",
   "A192KW", or "A256KW" are respectively used in this case.

   An example using this algorithm is shown in Appendix A.3 of [JWE].

4.6.  Direct Encryption with a Shared Symmetric Key

   This section defines the specifics of directly performing symmetric
   key encryption without performing a key wrapping step.  In this case,
   the shared symmetric key is used directly as the Content Encryption
   Key (CEK) value for the "enc" algorithm.  An empty octet sequence is
   used as the JWE Encrypted Key value.  The "alg" header parameter
   value "dir" is used in this case.

4.7.  Key Agreement with Elliptic Curve Diffie-Hellman Ephemeral Static
      (ECDH-ES)

   This section defines the specifics of key agreement with Elliptic
   Curve Diffie-Hellman Ephemeral Static [RFC6090], and using the Concat
   KDF, as defined in Section 5.8.1 of [NIST.800-56A].  The key
   agreement result can be used in one of two ways:




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   1.  directly as the Content Encryption Key (CEK) for the "enc"
       algorithm, in the Direct Key Agreement mode, or

   2.  as a symmetric key used to wrap the CEK with either the "A128KW",
       "A192KW", or "A256KW" algorithms, in the Key Agreement with Key
       Wrapping mode.

   The "alg" header parameter value "ECDH-ES" is used in the Direct Key
   Agreement mode and the values "ECDH-ES+A128KW", "ECDH-ES+A192KW", or
   "ECDH-ES+A256KW" are used in the Key Agreement with Key Wrapping
   mode.

   In the Direct Key Agreement case, the output of the Concat KDF MUST
   be a key of the same length as that used by the "enc" algorithm; in
   this case, the empty octet sequence is used as the JWE Encrypted Key
   value.  In the Key Agreement with Key Wrapping case, the output of
   the Concat KDF MUST be a key of the length needed for the specified
   key wrapping algorithm, one of 128, 192, or 256 bits respectively.

   A new ephemeral public key value MUST be generated for each key
   agreement transaction.

4.7.1.  Header Parameters Used for ECDH Key Agreement

   The following Header Parameter Names are reserved and are used for
   key agreement as defined below.  They MAY also be used for other
   algorithms if so specified by those algorithm parameter definitions.

4.7.1.1.  "epk" (Ephemeral Public Key) Header Parameter

   The "epk" (ephemeral public key) value created by the originator for
   the use in key agreement algorithms.  This key is represented as a
   JSON Web Key [JWK] bare public key value.  This Header Parameter is
   REQUIRED and MUST be understood and processed by implementations when
   these algorithms are used.

4.7.1.2.  "apu" (Agreement PartyUInfo) Header Parameter

   The "apu" (agreement PartyUInfo) value for key agreement algorithms
   using it (such as "ECDH-ES"), represented as a base64url encoded
   string.  When used, the PartyUInfo value contains information about
   the sender.  Use of this Header Parameter is OPTIONAL.  This Header
   Parameter MUST be understood and processed by implementations when
   these algorithms are used.







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4.7.1.3.  "apv" (Agreement PartyVInfo) Header Parameter

   The "apv" (agreement PartyVInfo) value for key agreement algorithms
   using it (such as "ECDH-ES"), represented as a base64url encoded
   string.  When used, the PartyVInfo value contains information about
   the receiver.  Use of this Header Parameter is OPTIONAL.  This Header
   Parameter MUST be understood and processed by implementations when
   these algorithms are used.

4.7.2.  Key Derivation for ECDH Key Agreement

   The key derivation process derives the agreed upon key from the
   shared secret Z established through the ECDH algorithm, per Section
   6.2.2.2 of [NIST.800-56A].

   Key derivation is performed using the Concat KDF, as defined in
   Section 5.8.1 of [NIST.800-56A], where the Digest Method is SHA-256.
   The Concat KDF parameters are set as follows:

   Z  This is set to the representation of the shared secret Z as an
      octet sequence.

   keydatalen  This is set to the number of bits in the desired output
      key.  For "ECDH-ES", this is length of the key used by the "enc"
      algorithm.  For "ECDH-ES+A128KW", "ECDH-ES+A192KW", and
      "ECDH-ES+A256KW", this is 128, 192, and 256, respectively.

   AlgorithmID  In the Direct Key Agreement case, this is set to the
      octets of the UTF-8 representation of the "enc" header parameter
      value.  In the Key Agreement with Key Wrapping case, this is set
      to the octets of the UTF-8 representation of the "alg" header
      parameter value.

   PartyUInfo  The PartyUInfo value is of the form Datalen || Data,
      where Data is a variable-length string of zero or more octets, and
      Datalen is a fixed-length, big endian 32 bit counter that
      indicates the length (in octets) of Data, with || being
      concatenation.  If an "apu" (agreement PartyUInfo) header
      parameter is present, Data is set to the result of base64url
      decoding the "apu" value and Datalen is set to the number of
      octets in Data.  Otherwise, Datalen is set to 0 and Data is set to
      the empty octet sequence.

   PartyVInfo  The PartyVInfo value is of the form Datalen || Data,
      where Data is a variable-length string of zero or more octets, and
      Datalen is a fixed-length, big endian 32 bit counter that
      indicates the length (in octets) of Data, with || being
      concatenation.  If an "apv" (agreement PartyVInfo) header



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      parameter is present, Data is set to the result of base64url
      decoding the "apv" value and Datalen is set to the number of
      octets in Data.  Otherwise, Datalen is set to 0 and Data is set to
      the empty octet sequence.

   SuppPubInfo  This is set to the keydatalen represented as a 32 bit
      big endian integer.

   SuppPrivInfo  This is set to the empty octet sequence.

   See Appendix D for an example key agreement computation using this
   method.

   Note: The Diffie-Hellman Key Agreement Method [RFC2631] uses a key
   derivation function similar to the Concat KDF, but with fewer
   parameters.  Rather than having separate PartyUInfo and PartyVInfo
   parameters, it uses a single PartyAInfo parameter, which is a random
   string provided by the sender, that contains 512 bits of information,
   when provided.  It has no SuppPrivInfo parameter.  Should it be
   appropriate for the application, key agreement can be performed in a
   manner akin to RFC 2631 by using the PartyAInfo value as the "apu"
   (Agreement PartyUInfo) header parameter value, when provided, and by
   using no "apv" (Agreement PartyVInfo) header parameter.

4.8.  Key Encryption with AES GCM

   This section defines the specifics of encrypting a JWE Content
   Encryption Key (CEK) with Advanced Encryption Standard (AES) in
   Galois/Counter Mode (GCM) [AES] [NIST.800-38D] using 128, 192, or 256
   bit keys.  The "alg" header parameter values "A128GCMKW",
   "A192GCMKW", or "A256GCMKW" are respectively used in this case.

   Use of an Initialization Vector of size 96 bits is REQUIRED with this
   algorithm.  The Initialization Vector is represented in base64url
   encoded form as the "iv" (initialization vector) header parameter
   value.

   The Additional Authenticated Data value used is the empty octet
   string.

   The requested size of the Authentication Tag output MUST be 128 bits,
   regardless of the key size.

   The JWE Encrypted Key value is the Ciphertext output.

   The Authentication Tag output is represented in base64url encoded
   form as the "tag" (authentication tag) header parameter value.




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4.8.1.  Header Parameters Used for AES GCM Key Encryption

   The following Header Parameters are used for AES GCM key encryption.
   They MAY also be used by other algorithms if so specified by those
   algorithm parameter definitions.

4.8.1.1.  "iv" (Initialization Vector) Header Parameter

   The "iv" (initialization vector) header parameter value is the
   base64url encoded representation of the Initialization Vector value
   used for the key encryption operation.  This Header Parameter is
   REQUIRED and MUST be understood and processed by implementations when
   these algorithms are used.

4.8.1.2.  "tag" (Authentication Tag) Header Parameter

   The "tag" (authentication tag) header parameter value is the
   base64url encoded representation of the Authentication Tag value
   resulting from the key encryption operation.  This Header Parameter
   is REQUIRED and MUST be understood and processed by implementations
   when these algorithms are used.

4.9.  Key Encryption with PBES2

   The "PBES2-HS256+A128KW", "PBES2-HS256+A192KW", and
   "PBES2-HS256+A256KW" algorithms are used to encrypt a JWE Content
   Master Key using a user-supplied password to derive the key
   encryption key.  With these algorithms, the derived key is used to
   encrypt the JWE Content Master Key. These algorithms combine a key
   derivation function with an encryption scheme to encrypt the JWE
   Content Master Key according to PBES2 from Section 6.2 of [RFC2898].

   These algorithms use HMAC SHA-256 as the Pseudo-Random Function (PRF)
   and AES Key Wrap [RFC3394] for the encryption scheme.  The salt (s)
   and iteration count (c) parameters MUST be provided as the "p2s" and
   "p2c" header parameter values.  The algorithms respectively use 128,
   192, and 256 bit AES Key Wrap keys.  Their derived-key lengths
   (dkLen) respectively are 16, 24, and 32 octets.

4.9.1.  Header Parameters Used for PBES2 Key Encryption

   The following Header Parameters are used for Key Encryption with
   PBES2.

4.9.1.1.  "p2s" (PBES2 salt) Parameter

   The "p2s" (PBES2 salt) header parameter contains the PBKDF2 salt
   value (s) as a base64url encoded string.  This value MUST NOT be the



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   empty string.  This Header Parameter is REQUIRED and MUST be
   understood and processed by implementations when these algorithms are
   used.

   The salt expands the possible keys that can be derived from a given
   password.  [RFC2898] originally recommended a minimum salt length of
   8 octets (since there is no concern here of a derived key being re-
   used for different purposes).  The salt MUST be generated randomly;
   see [RFC4086] for considerations on generating random values.

4.9.1.2.  "p2c" (PBES2 count) Parameter

   The "p2c" (PBES2 count) header parameter contains the PBKDF2
   iteration count (c), as an integer.  This value MUST NOT be less than
   1, as per [RFC2898].  This Header Parameter is REQUIRED and MUST be
   understood and processed by implementations when these algorithms are
   used.

   The iteration count adds computational expense, ideally compounded by
   the possible range of keys introduced by the salt.  [RFC2898]
   originally recommended a minimum iteration count of 1000.

4.10.  AES_CBC_HMAC_SHA2 Algorithms

   This section defines a family of authenticated encryption algorithms
   built using a composition of Advanced Encryption Standard (AES) in
   Cipher Block Chaining (CBC) mode with PKCS #5 padding [AES]
   [NIST.800-38A] operations and HMAC [RFC2104] [SHS] operations.  This
   algorithm family is called AES_CBC_HMAC_SHA2.  It also defines three
   instances of this family, the first using 128 bit CBC keys and HMAC
   SHA-256, the second using 192 bit CBC keys and HMAC SHA-384, and the
   third using 256 bit CBC keys and HMAC SHA-512.  Test cases for these
   algorithms can be found in Appendix C.

   These algorithms are based upon Authenticated Encryption with AES-CBC
   and HMAC-SHA [I-D.mcgrew-aead-aes-cbc-hmac-sha2], performing the same
   cryptographic computations, but with the Initialization Vector and
   Authentication Tag values remaining separate, rather than being
   concatenated with the Ciphertext value in the output representation.
   This option is discussed in Appendix B of that specification.  This
   algorithm family is a generalization of the algorithm family in
   [I-D.mcgrew-aead-aes-cbc-hmac-sha2], and can be used to implement
   those algorithms.

4.10.1.  Conventions Used in Defining AES_CBC_HMAC_SHA2

   We use the following notational conventions.




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      CBC-PKCS5-ENC(X, P) denotes the AES CBC encryption of P using PKCS
      #5 padding using the cipher with the key X.

      MAC(Y, M) denotes the application of the Message Authentication
      Code (MAC) to the message M, using the key Y.

      The concatenation of two octet strings A and B is denoted as
      A || B.

4.10.2.  Generic AES_CBC_HMAC_SHA2 Algorithm

   This section defines AES_CBC_HMAC_SHA2 in a manner that is
   independent of the AES CBC key size or hash function to be used.
   Section 4.10.2.1 and Section 4.10.2.2 define the generic encryption
   and decryption algorithms.  Section 4.10.3 and Section 4.10.5 define
   instances of AES_CBC_HMAC_SHA2 that specify those details.

4.10.2.1.  AES_CBC_HMAC_SHA2 Encryption

   The authenticated encryption algorithm takes as input four octet
   strings: a secret key K, a plaintext P, associated data A, and an
   initialization vector IV.  The authenticated ciphertext value E and
   the authentication tag value T are provided as outputs.  The data in
   the plaintext are encrypted and authenticated, and the associated
   data are authenticated, but not encrypted.

   The encryption process is as follows, or uses an equivalent set of
   steps:

   1.  The secondary keys MAC_KEY and ENC_KEY are generated from the
       input key K as follows.  Each of these two keys is an octet
       string.

          MAC_KEY consists of the initial MAC_KEY_LEN octets of K, in
          order.

          ENC_KEY consists of the final ENC_KEY_LEN octets of K, in
          order.

       Here we denote the number of octets in the MAC_KEY as
       MAC_KEY_LEN, and the number of octets in ENC_KEY as ENC_KEY_LEN;
       the values of these parameters are specified by the AEAD
       algorithms (in Section 4.10.3 and Section 4.10.5).  The number of
       octets in the input key K is the sum of MAC_KEY_LEN and
       ENC_KEY_LEN.  When generating the secondary keys from K, MAC_KEY
       and ENC_KEY MUST NOT overlap.  Note that the MAC key comes before
       the encryption key in the input key K; this is in the opposite
       order of the algorithm names in the identifier



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       "AES_CBC_HMAC_SHA2".

   2.  The Initialization Vector (IV) used is a 128 bit value generated
       randomly or pseudorandomly for use in the cipher.

   3.  The plaintext is CBC encrypted using PKCS #5 padding using
       ENC_KEY as the key, and the IV.  We denote the ciphertext output
       from this step as E.

   4.  The octet string AL is equal to the number of bits in A expressed
       as a 64-bit unsigned integer in network byte order.

   5.  A message authentication tag T is computed by applying HMAC
       [RFC2104] to the following data, in order:

          the associated data A,

          the initialization vector IV,

          the ciphertext E computed in the previous step, and

          the octet string AL defined above.

       The string MAC_KEY is used as the MAC key.  We denote the output
       of the MAC computed in this step as M. The first T_LEN bits of M
       are used as T.

   6.  The Ciphertext E and the Authentication Tag T are returned as the
       outputs of the authenticated encryption.

   The encryption process can be illustrated as follows.  Here K, P, A,
   IV, and E denote the key, plaintext, associated data, initialization
   vector, and ciphertext, respectively.

      MAC_KEY = initial MAC_KEY_LEN bytes of K,

      ENC_KEY = final ENC_KEY_LEN bytes of K,

      E = CBC-PKCS5-ENC(ENC_KEY, P),

      M = MAC(MAC_KEY, A || IV || E || AL),

      T = initial T_LEN bytes of M.








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4.10.2.2.  AES_CBC_HMAC_SHA2 Decryption

   The authenticated decryption operation has four inputs: K, A, E, and
   T as defined above.  It has only a single output, either a plaintext
   value P or a special symbol FAIL that indicates that the inputs are
   not authentic.  The authenticated decryption algorithm is as follows,
   or uses an equivalent set of steps:

   1.  The secondary keys MAC_KEY and ENC_KEY are generated from the
       input key K as in Step 1 of Section 4.10.2.1.

   2.  The integrity and authenticity of A and E are checked by
       computing an HMAC with the inputs as in Step 5 of
       Section 4.10.2.1.  The value T, from the previous step, is
       compared to the first MAC_KEY length bits of the HMAC output.  If
       those values are identical, then A and E are considered valid,
       and processing is continued.  Otherwise, all of the data used in
       the MAC validation are discarded, and the AEAD decryption
       operation returns an indication that it failed, and the operation
       halts.  (But see Section 10 of [JWE] for security considerations
       on thwarting timing attacks.)

   3.  The value E is decrypted and the PKCS #5 padding is removed.  The
       value IV is used as the initialization vector.  The value ENC_KEY
       is used as the decryption key.

   4.  The plaintext value is returned.

4.10.3.  AES_128_CBC_HMAC_SHA_256

   This algorithm is a concrete instantiation of the generic
   AES_CBC_HMAC_SHA2 algorithm above.  It uses the HMAC message
   authentication code [RFC2104] with the SHA-256 hash function [SHS] to
   provide message authentication, with the HMAC output truncated to 128
   bits, corresponding to the HMAC-SHA-256-128 algorithm defined in
   [RFC4868].  For encryption, it uses AES in the Cipher Block Chaining
   (CBC) mode of operation as defined in Section 6.2 of [NIST.800-38A],
   with PKCS #5 padding.

   The input key K is 32 octets long.

   The AES CBC IV is 16 octets long.  ENC_KEY_LEN is 16 octets.

   The SHA-256 hash algorithm is used in HMAC.  MAC_KEY_LEN is 16
   octets.  The HMAC-SHA-256 output is truncated to T_LEN=16 octets, by
   stripping off the final 16 octets.





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4.10.4.  AES_192_CBC_HMAC_SHA_384

   AES_192_CBC_HMAC_SHA_384 is based on AES_128_CBC_HMAC_SHA_256, but
   with the following differences:

      A 192 bit AES CBC key is used instead of 128.

      SHA-384 is used in HMAC instead of SHA-256.

      ENC_KEY_LEN is 24 octets instead of 16.

      MAC_KEY_LEN is 24 octets instead of 16.

      The length of the input key K is 48 octets instead of 32.

      The HMAC SHA-384 value is truncated to T_LEN=24 octets instead of
      16.

4.10.5.  AES_256_CBC_HMAC_SHA_512

   AES_256_CBC_HMAC_SHA_512 is based on AES_128_CBC_HMAC_SHA_256, but
   with the following differences:

      A 256 bit AES CBC key is used instead of 128.

      SHA-512 is used in HMAC instead of SHA-256.

      ENC_KEY_LEN is 32 octets instead of 16.

      MAC_KEY_LEN is 32 octets instead of 16.

      The length of the input key K is 64 octets instead of 32.

      The HMAC SHA-512 value is truncated to T_LEN=32 octets instead of
      16.

4.10.6.  Plaintext Encryption with AES_CBC_HMAC_SHA2

   The algorithm value "A128CBC-HS256" is used as the "alg" value when
   using AES_128_CBC_HMAC_SHA_256 with JWE.  The algorithm value
   "A192CBC-HS384" is used as the "alg" value when using
   AES_192_CBC_HMAC_SHA_384 with JWE.  The algorithm value
   "A256CBC-HS512" is used as the "alg" value when using
   AES_256_CBC_HMAC_SHA_512 with JWE.  The Additional Authenticated Data
   value used is the octets of the ASCII representation of the Encoded
   JWE Header value.  The JWE Initialization Vector value used is the IV
   value.




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4.11.  Plaintext Encryption with AES GCM

   This section defines the specifics of encrypting the JWE Plaintext
   with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM)
   [AES] [NIST.800-38D] using 128, 192, or 256 bit keys.  The "enc"
   header parameter values "A128GCM", "A192GCM", or "A256GCM" are
   respectively used in this case.

   The CEK is used as the encryption key.

   Use of an initialization vector of size 96 bits is REQUIRED with this
   algorithm.

   The Additional Authenticated Data value used is the octets of the
   ASCII representation of the Encoded JWE Header value.

   The requested size of the Authentication Tag output MUST be 128 bits,
   regardless of the key size.

   The JWE Authentication Tag is set to be the Authentication Tag value
   produced by the encryption.  During decryption, the received JWE
   Authentication Tag is used as the Authentication Tag value.

   An example using this algorithm is shown in Appendix A.1 of [JWE].

4.12.  Additional Encryption Algorithms and Parameters

   Additional algorithms MAY be used to protect JWEs with corresponding
   "alg" (algorithm) and "enc" (encryption method) header parameter
   values being defined to refer to them.  New "alg" and "enc" header
   parameter values SHOULD either be registered in the IANA JSON Web
   Signature and Encryption Algorithms registry Section 6.1 or be a
   value that contains a Collision Resistant Namespace.  In particular,
   it is permissible to use the algorithm identifiers defined in XML
   Encryption [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1
   [W3C.CR-xmlenc-core1-20120313], and related specifications as "alg"
   and "enc" values.

   As indicated by the common registry, JWSs and JWEs share a common
   "alg" value space.  The values used by the two specifications MUST be
   distinct, as the "alg" value can be used to determine whether the
   object is a JWS or JWE.

   Likewise, additional reserved Header Parameter Names can be defined
   via the IANA JSON Web Signature and Encryption Header Parameters
   registry [JWS].  As indicated by the common registry, JWSs and JWEs
   share a common header parameter space; when a parameter is used by
   both specifications, its usage must be compatible between the



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   specifications.


5.  Cryptographic Algorithms for JWK

   A JSON Web Key (JWK) [JWK] is a JavaScript Object Notation (JSON)
   [RFC4627] data structure that represents a cryptographic key.  A JSON
   Web Key Set (JWK Set) is a JSON data structure for representing a set
   of JWKs.  This section specifies a set of key types to be used for
   those keys and the key type specific parameters for representing
   those keys.  Parameters are defined for public, private, and
   symmetric keys.

5.1.  "kty" (Key Type) Parameter Values for JWK

   The table below is the set of "kty" (key type) parameter values that
   are defined by this specification for use in JWKs.

   +-------------+----------------------------------+------------------+
   | kty         | Key Type                         | Implementation   |
   | Parameter   |                                  | Requirements     |
   | Value       |                                  |                  |
   +-------------+----------------------------------+------------------+
   | EC          | Elliptic Curve [DSS] key type    | RECOMMENDED+     |
   | RSA         | RSA [RFC3447] key type           | REQUIRED         |
   | oct         | Octet sequence key type (used to | RECOMMENDED+     |
   |             | represent symmetric keys)        |                  |
   +-------------+----------------------------------+------------------+

   All the names are short because a core goal of JWK is for the
   representations to be compact.  However, there is no a priori length
   restriction on "kty" values.

   The use of "+" in the Implementation Requirements indicates that the
   requirement strength is likely to be increased in a future version of
   the specification.

5.2.  JWK Parameters for Elliptic Curve Keys

   JWKs can represent Elliptic Curve [DSS] keys.  In this case, the
   "kty" member value MUST be "EC".

5.2.1.  JWK Parameters for Elliptic Curve Public Keys

   These members MUST be present for Elliptic Curve public keys:






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5.2.1.1.  "crv" (Curve) Parameter

   The "crv" (curve) member identifies the cryptographic curve used with
   the key.  Curve values from [DSS] used by this specification are:

   o  "P-256"

   o  "P-384"

   o  "P-521"

   Additional "crv" values MAY be used, provided they are understood by
   implementations using that Elliptic Curve key.  The "crv" value is a
   case sensitive string.

5.2.1.2.  "x" (X Coordinate) Parameter

   The "x" (x coordinate) member contains the x coordinate for the
   elliptic curve point.  It is represented as the base64url encoding of
   the coordinate's big endian representation as an octet sequence.  The
   array representation MUST NOT be shortened to omit any leading zero
   octets contained in the value.  For instance, when representing 521
   bit integers, the octet sequence to be base64url encoded MUST contain
   66 octets, including any leading zero octets.

5.2.1.3.  "y" (Y Coordinate) Parameter

   The "y" (y coordinate) member contains the y coordinate for the
   elliptic curve point.  It is represented as the base64url encoding of
   the coordinate's big endian representation as an octet sequence.  The
   array representation MUST NOT be shortened to omit any leading zero
   octets contained in the value.  For instance, when representing 521
   bit integers, the octet sequence to be base64url encoded MUST contain
   66 octets, including any leading zero octets.

5.2.2.  JWK Parameters for Elliptic Curve Private Keys

   In addition to the members used to represent Elliptic Curve public
   keys, the following member MUST be present to represent Elliptic
   Curve private keys:

5.2.2.1.  "d" (ECC Private Key) Parameter

   The "d" (ECC private key) member contains the Elliptic Curve private
   key value.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as an octet sequence.  The
   array representation MUST NOT be shortened to omit any leading zero
   octets.  For instance, when representing 521 bit integers, the octet



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   sequence to be base64url encoded MUST contain 66 octets, including
   any leading zero octets.

5.3.  JWK Parameters for RSA Keys

   JWKs can represent RSA [RFC3447] keys.  In this case, the "kty"
   member value MUST be "RSA".

5.3.1.  JWK Parameters for RSA Public Keys

   These members MUST be present for RSA public keys:

5.3.1.1.  "n" (Modulus) Parameter

   The "n" (modulus) member contains the modulus value for the RSA
   public key.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as an octet sequence.  The
   array representation MUST NOT be shortened to omit any leading zero
   octets.  For instance, when representing 2048 bit integers, the octet
   sequence to be base64url encoded MUST contain 256 octets, including
   any leading zero octets.

5.3.1.2.  "e" (Exponent) Parameter

   The "e" (exponent) member contains the exponent value for the RSA
   public key.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as an octet sequence.  The
   array representation MUST utilize the minimum number of octets to
   represent the value.  For instance, when representing the value
   65537, the octet sequence to be base64url encoded MUST consist of the
   three octets [1, 0, 1].

5.3.2.  JWK Parameters for RSA Private Keys

   In addition to the members used to represent RSA public keys, the
   following members are used to represent RSA private keys.  The
   parameter "d" is REQUIRED for RSA private keys.  The others enable
   optimizations and are RECOMMENDED.  If any of the others are present
   then all MUST be present, with the exception of "oth", which MUST
   only be present when more than two prime factors were used.

5.3.2.1.  "d" (Private Exponent) Parameter

   The "d" (private exponent) member contains the private exponent value
   for the RSA private key.  It is represented as the base64url encoding
   of the value's unsigned big endian representation as an octet
   sequence.  The array representation MUST NOT be shortened to omit any
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   integers, the octet sequence to be base64url encoded MUST contain 256
   octets, including any leading zero octets.

5.3.2.2.  "p" (First Prime Factor) Parameter

   The "p" (first prime factor) member contains the first prime factor,
   a positive integer.  It is represented as the base64url encoding of
   the value's unsigned big endian representation as an octet sequence.

5.3.2.3.  "q" (Second Prime Factor) Parameter

   The "q" (second prime factor) member contains the second prime
   factor, a positive integer.  It is represented as the base64url
   encoding of the value's unsigned big endian representation as an
   octet sequence.

5.3.2.4.  "dp" (First Factor CRT Exponent) Parameter

   The "dp" (first factor CRT exponent) member contains the Chinese
   Remainder Theorem (CRT) exponent of the first factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as an octet sequence.

5.3.2.5.  "dq" (Second Factor CRT Exponent) Parameter

   The "dq" (second factor CRT exponent) member contains the Chinese
   Remainder Theorem (CRT) exponent of the second factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as an octet sequence.

5.3.2.6.  "qi" (First CRT Coefficient) Parameter

   The "dp" (first CRT coefficient) member contains the Chinese
   Remainder Theorem (CRT) coefficient of the second factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as an octet sequence.

5.3.2.7.  "oth" (Other Primes Info) Parameter

   The "oth" (other primes info) member contains an array of information
   about any third and subsequent primes, should they exist.  When only
   two primes have been used (the normal case), this parameter MUST be
   omitted.  When three or more primes have been used, the number of
   array elements MUST be the number of primes used minus two.  Each
   array element MUST be an object with the following members:






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5.3.2.7.1.  "r" (Prime Factor)

   The "r" (prime factor) parameter within an "oth" array member
   represents the value of a subsequent prime factor, a positive
   integer.  It is represented as the base64url encoding of the value's
   unsigned big endian representation as an octet sequence.

5.3.2.7.2.  "d" (Factor CRT Exponent)

   The "d" (Factor CRT Exponent) parameter within an "oth" array member
   represents the CRT exponent of the corresponding prime factor, a
   positive integer.  It is represented as the base64url encoding of the
   value's unsigned big endian representation as an octet sequence.

5.3.2.7.3.  "t" (Factor CRT Coefficient)

   The "t" (factor CRT coefficient) parameter within an "oth" array
   member represents the CRT coefficient of the corresponding prime
   factor, a positive integer.  It is represented as the base64url
   encoding of the value's unsigned big endian representation as an
   octet sequence.

5.3.3.  JWK Parameters for Symmetric Keys

   When the JWK "kty" member value is "oct" (octet sequence), the
   following member is used to represent a symmetric key (or another key
   whose value is a single octet sequence):

5.3.3.1.  "k" (Key Value) Parameter

   The "k" (key value) member contains the value of the symmetric (or
   other single-valued) key.  It is represented as the base64url
   encoding of the octet sequence containing the key value.

5.4.  Additional Key Types and Parameters

   Keys using additional key types can be represented using JWK data
   structures with corresponding "kty" (key type) parameter values being
   defined to refer to them.  New "kty" parameter values SHOULD either
   be registered in the IANA JSON Web Key Types registry Section 6.2 or
   be a value that contains a Collision Resistant Namespace.

   Likewise, parameters for representing keys for additional key types
   or additional key properties SHOULD either be registered in the IANA
   JSON Web Key Parameters registry [JWK] or be a value that contains a
   Collision Resistant Namespace.





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6.  IANA Considerations

   The following registration procedure is used for all the registries
   established by this specification.

   Values are registered with a Specification Required [RFC5226] after a
   two-week review period on the [TBD]@ietf.org mailing list, on the
   advice of one or more Designated Experts.  However, to allow for the
   allocation of values prior to publication, the Designated Expert(s)
   may approve registration once they are satisfied that such a
   specification will be published.

   Registration requests must be sent to the [TBD]@ietf.org mailing list
   for review and comment, with an appropriate subject (e.g., "Request
   for access token type: example"). [[ Note to RFC-EDITOR: The name of
   the mailing list should be determined in consultation with the IESG
   and IANA.  Suggested name: jose-reg-review. ]]

   Within the review period, the Designated Expert(s) will either
   approve or deny the registration request, communicating this decision
   to the review list and IANA.  Denials should include an explanation
   and, if applicable, suggestions as to how to make the request
   successful.

   IANA must only accept registry updates from the Designated Expert(s)
   and should direct all requests for registration to the review mailing
   list.

6.1.  JSON Web Signature and Encryption Algorithms Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Algorithms registry for values of the JWS and JWE "alg"
   (algorithm) and "enc" (encryption method) header parameters.  The
   registry records the algorithm name, the algorithm usage locations
   from the set "alg" and "enc", implementation requirements, and a
   reference to the specification that defines it.  The same algorithm
   name MAY be registered multiple times, provided that the sets of
   usage locations are disjoint.  The implementation requirements of an
   algorithm MAY be changed over time by the Designated Experts(s) as
   the cryptographic landscape evolves, for instance, to change the
   status of an algorithm to DEPRECATED, or to change the status of an
   algorithm from OPTIONAL to RECOMMENDED or REQUIRED.

6.1.1.  Template







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   Algorithm Name:
      The name requested (e.g., "example").  This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted.

   Algorithm Usage Location(s):
      The algorithm usage, which must be one or more of the values "alg"
      or "enc".

   Implementation Requirements:
      The algorithm implementation requirements, which must be one the
      words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED.  Optionally,
      the word can be followed by a "+" or "-".  The use of "+"
      indicates that the requirement strength is likely to be increased
      in a future version of the specification.  The use of "-"
      indicates that the requirement strength is likely to be decreased
      in a future version of the specification.

   Change Controller:
      For Standards Track RFCs, state "IETF".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      email address, home page URI) may also be included.

   Specification Document(s):
      Reference to the document(s) that specify the parameter,
      preferably including URI(s) that can be used to retrieve copies of
      the document(s).  An indication of the relevant sections may also
      be included but is not required.

6.1.2.  Initial Registry Contents

   o  Algorithm Name: "HS256"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "HS384"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "HS512"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL





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   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "RS256"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "RS384"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "RS512"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "ES256"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED+
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "ES384"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "ES512"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "PS256"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "PS384"





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   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "PS512"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "none"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 3.1 of [[ this document ]]

   o  Algorithm Name: "RSA1_5"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "RSA-OAEP"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "A128KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "A192KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "A256KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]





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   o  Algorithm Name: "dir"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "ECDH-ES"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED+
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "ECDH-ES+A128KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "ECDH-ES+A192KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "ECDH-ES+A256KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.1 of [[ this document ]]

   o  Algorithm Name: "A128GCMKW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.8 of [[ this document ]]

   o  Algorithm Name: "A192GCMKW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.8 of [[ this document ]]

   o  Algorithm Name: "A256GCMKW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF





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   o  Specification Document(s): Section 4.8 of [[ this document ]]

   o  Algorithm Name: "PBES2-HS256+A128KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.9 of [[ this document ]]

   o  Algorithm Name: "PBES2-HS256+A192KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.9 of [[ this document ]]

   o  Algorithm Name: "PBES2-HS256+A256KW"
   o  Algorithm Usage Location(s): "alg"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.9 of [[ this document ]]

   o  Algorithm Name: "A128CBC-HS256"
   o  Algorithm Usage Location(s): "enc"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

   o  Algorithm Name: "A192CBC-HS384"
   o  Algorithm Usage Location(s): "enc"
   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

   o  Algorithm Name: "A256CBC-HS512"
   o  Algorithm Usage Location(s): "enc"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

   o  Algorithm Name: "A128GCM"
   o  Algorithm Usage Location(s): "enc"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

   o  Algorithm Name: "A192GCM"
   o  Algorithm Usage Location(s): "enc"





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   o  Implementation Requirements: OPTIONAL
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

   o  Algorithm Name: "A256GCM"
   o  Algorithm Usage Location(s): "enc"
   o  Implementation Requirements: RECOMMENDED
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.2 of [[ this document ]]

6.2.  JSON Web Key Types Registry

   This specification establishes the IANA JSON Web Key Types registry
   for values of the JWK "kty" (key type) parameter.  The registry
   records the "kty" value and a reference to the specification that
   defines it.  This specification registers the values defined in
   Section 5.1.

6.2.1.  Registration Template

   "kty" Parameter Value:
      The name requested (e.g., "example").  This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted.

   Change Controller:
      For Standards Track RFCs, state "IETF".  For others, give the name
      of the responsible party.  Other details (e.g., postal address,
      email address, home page URI) may also be included.

   Implementation Requirements:
      The algorithm implementation requirements, which must be one the
      words REQUIRED, RECOMMENDED, OPTIONAL, or DEPRECATED.  Optionally,
      the word can be followed by a "+" or "-".  The use of "+"
      indicates that the requirement strength is likely to be increased
      in a future version of the specification.  The use of "-"
      indicates that the requirement strength is likely to be decreased
      in a future version of the specification.

   Specification Document(s):
      Reference to the document(s) that specify the parameter,
      preferably including URI(s) that can be used to retrieve copies of
      the document(s).  An indication of the relevant sections may also
      be included but is not required.







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6.2.2.  Initial Registry Contents

   o  "kty" Parameter Value: "EC"
   o  Implementation Requirements: RECOMMENDED+
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.2 of [[ this document ]]

   o  "kty" Parameter Value: "RSA"
   o  Implementation Requirements: REQUIRED
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3 of [[ this document ]]

   o  "kty" Parameter Value: "oct"
   o  Implementation Requirements: RECOMMENDED+
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.3 of [[ this document ]]

6.3.  JSON Web Key Parameters Registration

   This specification registers the parameter names defined in Sections
   5.2, 5.3, and 5.3.3 in the IANA JSON Web Key Parameters registry
   [JWK].

6.3.1.  Registry Contents

   o  Parameter Name: "crv"
   o  Parameter Information Class: Public
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.2.1.1 of [[ this document ]]

   o  Parameter Name: "x"
   o  Parameter Information Class: Public
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.2.1.2 of [[ this document ]]

   o  Parameter Name: "y"
   o  Parameter Information Class: Public
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.2.1.3 of [[ this document ]]

   o  Parameter Name: "d"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.2.2.1 of [[ this document ]]

   o  Parameter Name: "n"





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   o  Parameter Information Class: Public
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.1.1 of [[ this document ]]

   o  Parameter Name: "e"
   o  Parameter Information Class: Public
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.1.2 of [[ this document ]]

   o  Parameter Name: "d"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.1 of [[ this document ]]

   o  Parameter Name: "p"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.2 of [[ this document ]]

   o  Parameter Name: "q"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.3 of [[ this document ]]

   o  Parameter Name: "dp"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.4 of [[ this document ]]

   o  Parameter Name: "dq"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.5 of [[ this document ]]

   o  Parameter Name: "qi"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.6 of [[ this document ]]

   o  Parameter Name: "oth"
   o  Parameter Information Class: Private
   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.2.7 of [[ this document ]]

   o  Parameter Name: "k"
   o  Parameter Information Class: Private





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   o  Change Controller: IETF
   o  Specification Document(s): Section 5.3.3.1 of [[ this document ]]

6.4.  Registration of JWE Header Parameter Names

   This specification registers the Header Parameter Names defined in
   Section 4.7.1, Section 4.8.1, and Section 4.9.1 in the IANA JSON Web
   Signature and Encryption Header Parameters registry [JWS].

6.4.1.  Registry Contents

   o  Header Parameter Name: "epk"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.7.1.1 of [[ this document ]]

   o  Header Parameter Name: "apu"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.7.1.2 of [[ this document ]]

   o  Header Parameter Name: "apv"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.7.1.3 of [[ this document ]]

   o  Header Parameter Name: "iv"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.8.1.1 of [[ this document ]]

   o  Header Parameter Name: "tag"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.8.1.2 of [[ this document ]]

   o  Header Parameter Name: "p2s"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.9.1.1 of [[ this document ]]

   o  Header Parameter Name: "p2c"
   o  Header Parameter Usage Location(s): JWE
   o  Change Controller: IETF
   o  Specification Document(s): Section 4.9.1.2 of [[ this document ]]






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7.  Security Considerations

   All of the security issues faced by any cryptographic application
   must be faced by a JWS/JWE/JWK agent.  Among these issues are
   protecting the user's private and symmetric keys, preventing various
   attacks, and helping the user avoid mistakes such as inadvertently
   encrypting a message for the wrong recipient.  The entire list of
   security considerations is beyond the scope of this document, but
   some significant considerations are listed here.

   The security considerations in [AES], [DSS], [JWE], [JWK], [JWS],
   [NIST.800-38A], [NIST.800-38D], [NIST.800-56A], [RFC2104], [RFC3394],
   [RFC3447], [RFC5116], [RFC6090], and [SHS] apply to this
   specification.

   Eventually the algorithms and/or key sizes currently described in
   this specification will no longer be considered sufficiently secure
   and will be removed.  Therefore, implementers and deployments must be
   prepared for this eventuality.

   Many algorithms have associated security considerations related to
   key lifetimes and/or the number of times that a key may be used.
   Those security considerations continue to apply when using those
   algorithms with JOSE data structures.

   Algorithms of matching strengths should be used together whenever
   possible.  For instance, when AES Key Wrap is used with a given key
   size, using the same key size is recommended when AES GCM is also
   used.

   While Section 8 of RFC 3447 [RFC3447] explicitly calls for people not
   to adopt RSASSA-PKCS-v1_5 for new applications and instead requests
   that people transition to RSASSA-PSS, this specification does include
   RSASSA-PKCS-v1_5, for interoperability reasons, because it commonly
   implemented.

   Keys used with RSAES-PKCS1-v1_5 must follow the constraints in
   Section 7.2 of RFC 3447 [RFC3447].  In particular, keys with a low
   public key exponent value must not be used.

   Keys used with AES GCM must follow the constraints in Section 8.3 of
   [NIST.800-38D], which states: "The total number of invocations of the
   authenticated encryption function shall not exceed 2^32, including
   all IV lengths and all instances of the authenticated encryption
   function with the given key".  In accordance with this rule, AES GCM
   MUST NOT be used with the same key encryption key or with the same
   direct encryption key more than 2^32 times.




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   Plaintext JWSs (JWSs that use the "alg" value "none") provide no
   integrity protection.  Thus, they must only be used in contexts where
   the payload is secured by means other than a digital signature or MAC
   value, or need not be secured.

   Receiving agents that validate signatures and sending agents that
   encrypt messages need to be cautious of cryptographic processing
   usage when validating signatures and encrypting messages using keys
   larger than those mandated in this specification.  An attacker could
   send certificates with keys that would result in excessive
   cryptographic processing, for example, keys larger than those
   mandated in this specification, which could swamp the processing
   element.  Agents that use such keys without first validating the
   certificate to a trust anchor are advised to have some sort of
   cryptographic resource management system to prevent such attacks.

7.1.  Reusing Key Material when Encrypting Keys

   It is NOT RECOMMENDED to reuse the same key material (Key Encryption
   Key, Content Master Key, Initialization Vector, etc.) to encrypt
   multiple JWK or JWK Set objects, or to encrypt the same JWK or JWK
   Set object multiple times.  One suggestion for preventing re-use is
   to always generate a new set key material for each encryption
   operation, based on the considerations noted in this document as well
   as from [RFC4086].

7.2.  Password Considerations

   While convenient for end users, passwords are vulnerable to a number
   of attacks.  To help mitigate some of these limitations, this
   document applies principles from [RFC2898] to derive cryptographic
   keys from user-supplied passwords.

   However, the strength of the password still has a significant impact.
   A high-entry password has greater resistance to dictionary attacks.
   [NIST-800-63-1] contains guidelines for estimating password entropy,
   which can help applications and users generate stronger passwords.

   An ideal password is one that is as large (or larger) than the
   derived key length but less than the PRF's block size.  Passwords
   larger than the PRF's block size are first hashed, which reduces an
   attacker's effective search space to the length of the hash algorithm
   (32 octets for HMAC SHA-256).  It is RECOMMENDED that the password be
   no longer than 64 octets long for "PBES2-HS256+A256KW".

   Still, care needs to be taken in where and how password-based
   encryption is used.  Such algorithms MUST NOT be used where the
   attacker can make an indefinite number of attempts to circumvent the



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   protection.


8.  Internationalization Considerations

   Passwords obtained from users are likely to require preparation and
   normalization to account for differences of octet sequences generated
   by different input devices, locales, etc.  It is RECOMMENDED that
   applications to perform the steps outlined in
   [I-D.melnikov-precis-saslprepbis] to prepare a password supplied
   directly by a user before performing key derivation and encryption.


9.  References

9.1.  Normative References

   [AES]      National Institute of Standards and Technology (NIST),
              "Advanced Encryption Standard (AES)", FIPS PUB 197,
              November 2001.

   [DSS]      National Institute of Standards and Technology, "Digital
              Signature Standard (DSS)", FIPS PUB 186-3, June 2009.

   [I-D.melnikov-precis-saslprepbis]
              Saint-Andre, P. and A. Melnikov, "Preparation and
              Comparison of Internationalized Strings Representing
              Simple User Names and Passwords",
              draft-melnikov-precis-saslprepbis-04 (work in progress),
              September 2012.

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", draft-ietf-jose-json-web-encryption
              (work in progress), July 2013.

   [JWK]      Jones, M., "JSON Web Key (JWK)",
              draft-ietf-jose-json-web-key (work in progress),
              July 2013.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", draft-ietf-jose-json-web-signature (work
              in progress), July 2013.

   [NIST.800-38A]
              National Institute of Standards and Technology (NIST),
              "Recommendation for Block Cipher Modes of Operation",
              NIST PUB 800-38A, December 2001.




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   [NIST.800-38D]
              National Institute of Standards and Technology (NIST),
              "Recommendation for Block Cipher Modes of Operation:
              Galois/Counter Mode (GCM) and GMAC", NIST PUB 800-38D,
              December 2001.

   [NIST.800-56A]
              National Institute of Standards and Technology (NIST),
              "Recommendation for Pair-Wise Key Establishment Schemes
              Using Discrete Logarithm Cryptography", NIST Special
              Publication 800-56A, Revision 2, May 2013.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              February 1997.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2898]  Kaliski, B., "PKCS #5: Password-Based Cryptography
              Specification Version 2.0", RFC 2898, September 2000.

   [RFC3394]  Schaad, J. and R. Housley, "Advanced Encryption Standard
              (AES) Key Wrap Algorithm", RFC 3394, September 2002.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.

   [RFC4086]  Eastlake, D., Schiller, J., and S. Crocker, "Randomness
              Requirements for Security", BCP 106, RFC 4086, June 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
              384, and HMAC-SHA-512 with IPsec", RFC 4868, May 2007.

   [RFC5116]  McGrew, D., "An Interface and Algorithms for Authenticated
              Encryption", RFC 5116, January 2008.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC6090]  McGrew, D., Igoe, K., and M. Salter, "Fundamental Elliptic



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              Curve Cryptography Algorithms", RFC 6090, February 2011.

   [SHS]      National Institute of Standards and Technology, "Secure
              Hash Standard (SHS)", FIPS PUB 180-3, October 2008.

   [USASCII]  American National Standards Institute, "Coded Character
              Set -- 7-bit American Standard Code for Information
              Interchange", ANSI X3.4, 1986.

9.2.  Informative References

   [CanvasApp]
              Facebook, "Canvas Applications", 2010.

   [I-D.mcgrew-aead-aes-cbc-hmac-sha2]
              McGrew, D., Foley, J., and K. Paterson, "Authenticated
              Encryption with AES-CBC and HMAC-SHA",
              draft-mcgrew-aead-aes-cbc-hmac-sha2-02 (work in progress),
              July 2013.

   [I-D.miller-jose-jwe-protected-jwk]
              Miller, M., "Using JavaScript Object Notation (JSON) Web
              Encryption (JWE) for Protecting JSON Web Key (JWK)
              Objects", draft-miller-jose-jwe-protected-jwk-02 (work in
              progress), June 2013.

   [I-D.rescorla-jsms]
              Rescorla, E. and J. Hildebrand, "JavaScript Message
              Security Format", draft-rescorla-jsms-00 (work in
              progress), March 2011.

   [JCA]      Oracle, "Java Cryptography Architecture", 2011.

   [JSE]      Bradley, J. and N. Sakimura (editor), "JSON Simple
              Encryption", September 2010.

   [JSS]      Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
              September 2010.

   [MagicSignatures]
              Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
              Signatures", January 2011.

   [NIST-800-63-1]
              National Institute of Standards and Technology (NIST),
              "Electronic Authentication Guideline", NIST 800-63-1,
              December 2011.




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   [RFC2631]  Rescorla, E., "Diffie-Hellman Key Agreement Method",
              RFC 2631, June 1999.

   [RFC3275]  Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
              Language) XML-Signature Syntax and Processing", RFC 3275,
              March 2002.

   [RFC3447]  Jonsson, J. and B. Kaliski, "Public-Key Cryptography
              Standards (PKCS) #1: RSA Cryptography Specifications
              Version 2.1", RFC 3447, February 2003.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [W3C.CR-xmldsig-core2-20120124]
              Eastlake, D., Reagle, J., Yiu, K., Solo, D., Datta, P.,
              Hirsch, F., Cantor, S., and T. Roessler, "XML Signature
              Syntax and Processing Version 2.0", World Wide Web
              Consortium CR CR-xmldsig-core2-20120124, January 2012,
              <http://www.w3.org/TR/2012/CR-xmldsig-core2-20120124>.

   [W3C.CR-xmlenc-core1-20120313]
              Eastlake, D., Reagle, J., Roessler, T., and F. Hirsch,
              "XML Encryption Syntax and Processing Version 1.1", World
              Wide Web Consortium CR CR-xmlenc-core1-20120313,
              March 2012,
              <http://www.w3.org/TR/2012/CR-xmlenc-core1-20120313>.

   [W3C.REC-xmlenc-core-20021210]
              Eastlake, D. and J. Reagle, "XML Encryption Syntax and
              Processing", World Wide Web Consortium Recommendation REC-
              xmlenc-core-20021210, December 2002,
              <http://www.w3.org/TR/2002/REC-xmlenc-core-20021210>.


Appendix A.  Digital Signature/MAC Algorithm Identifier Cross-Reference

   This appendix contains a table cross-referencing the digital
   signature and MAC "alg" (algorithm) values used in this specification
   with the equivalent identifiers used by other standards and software
   packages.  See XML DSIG [RFC3275], XML DSIG 2.0
   [W3C.CR-xmldsig-core2-20120124], and Java Cryptography Architecture
   [JCA] for more information about the names defined by those
   documents.






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   +---------+----+---------------------------+----------+-------------+
   | Algorit | JW | XML DSIG                  | JCA      | OID         |
   | hm      | S  |                           |          |             |
   +---------+----+---------------------------+----------+-------------+
   | HMAC    | HS | http://www.w3.org/2001/04 | HmacSHA2 | 1.2.840.113 |
   | using   | 25 | /xmldsig-more#hmac-sha256 | 56       | 549.2.9     |
   | SHA-256 | 6  |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | HMAC    | HS | http://www.w3.org/2001/04 | HmacSHA3 | 1.2.840.113 |
   | using   | 38 | /xmldsig-more#hmac-sha384 | 84       | 549.2.10    |
   | SHA-384 | 4  |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | HMAC    | HS | http://www.w3.org/2001/04 | HmacSHA5 | 1.2.840.113 |
   | using   | 51 | /xmldsig-more#hmac-sha512 | 12       | 549.2.11    |
   | SHA-512 | 2  |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | RSASSA- | RS | http://www.w3.org/2001/04 | SHA256wi | 1.2.840.113 |
   | PKCS-v1 | 25 | /xmldsig-more#rsa-sha256  | thRSA    | 549.1.1.11  |
   | _5using | 6  |                           |          |             |
   |   SHA-2 |    |                           |          |             |
   | 56hash  |    |                           |          |             |
   |   algor |    |                           |          |             |
   | ithm    |    |                           |          |             |
   | RSASSA- | RS | http://www.w3.org/2001/04 | SHA384wi | 1.2.840.113 |
   | PKCS-v1 | 38 | /xmldsig-more#rsa-sha384  | thRSA    | 549.1.1.12  |
   | _5using | 4  |                           |          |             |
   |   SHA-3 |    |                           |          |             |
   | 84hash  |    |                           |          |             |
   |   algor |    |                           |          |             |
   | ithm    |    |                           |          |             |
   | RSASSA- | RS | http://www.w3.org/2001/04 | SHA512wi | 1.2.840.113 |
   | PKCS-v1 | 51 | /xmldsig-more#rsa-sha512  | thRSA    | 549.1.1.13  |
   | _5using | 2  |                           |          |             |
   |   SHA-5 |    |                           |          |             |
   | 12hash  |    |                           |          |             |
   |   algor |    |                           |          |             |
   | ithm    |    |                           |          |             |








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   | ECDSA   | ES | http://www.w3.org/2001/04 | SHA256wi | 1.2.840.100 |
   | using   | 25 | /xmldsig-more#ecdsa-sha25 | thECDSA  | 45.4.3.2    |
   | P-256   | 6  | 6                         |          |             |
   | curve   |    |                           |          |             |
   | and     |    |                           |          |             |
   | SHA-256 |    |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | ECDSA   | ES | http://www.w3.org/2001/04 | SHA384wi | 1.2.840.100 |
   | using   | 38 | /xmldsig-more#ecdsa-sha38 | thECDSA  | 45.4.3.3    |
   | P-384   | 4  | 4                         |          |             |
   | curve   |    |                           |          |             |
   | and     |    |                           |          |             |
   | SHA-384 |    |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | ECDSA   | ES | http://www.w3.org/2001/04 | SHA512wi | 1.2.840.100 |
   | using   | 51 | /xmldsig-more#ecdsa-sha51 | thECDSA  | 45.4.3.4    |
   | P-521   | 2  | 2                         |          |             |
   | curve   |    |                           |          |             |
   | and     |    |                           |          |             |
   | SHA-512 |    |                           |          |             |
   | hash    |    |                           |          |             |
   | algorit |    |                           |          |             |
   | hm      |    |                           |          |             |
   | RSASSA- | PS |                           |          |             |
   | PSS     | 25 |                           |          |             |
   |  using  | 6  |                           |          |             |
   |  SHA-25 |    |                           |          |             |
   | 6hash   |    |                           |          |             |
   |  algori |    |                           |          |             |
   | thm and |    |                           |          |             |
   |   MGF1  |    |                           |          |             |
   |   mask  |    |                           |          |             |
   |   gener |    |                           |          |             |
   | ation   |    |                           |          |             |
   |    func |    |                           |          |             |
   | tionwit |    |                           |          |             |
   | h   SHA |    |                           |          |             |
   | -256    |    |                           |          |             |









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   | RSASSA- | PS |                           |          |             |
   | PSS     | 38 |                           |          |             |
   |  using  | 4  |                           |          |             |
   |  SHA-38 |    |                           |          |             |
   | 4hash   |    |                           |          |             |
   |  algori |    |                           |          |             |
   | thm and |    |                           |          |             |
   |   MGF1  |    |                           |          |             |
   |   mask  |    |                           |          |             |
   |   gener |    |                           |          |             |
   | ation   |    |                           |          |             |
   |    func |    |                           |          |             |
   | tionwit |    |                           |          |             |
   | h   SHA |    |                           |          |             |
   | -384    |    |                           |          |             |
   | RSASSA- | PS |                           |          |             |
   | PSS     | 51 |                           |          |             |
   |  using  | 2  |                           |          |             |
   |  SHA-51 |    |                           |          |             |
   | 2hash   |    |                           |          |             |
   |  algori |    |                           |          |             |
   | thm and |    |                           |          |             |
   |   MGF1  |    |                           |          |             |
   |   mask  |    |                           |          |             |
   |   gener |    |                           |          |             |
   | ation   |    |                           |          |             |
   |    func |    |                           |          |             |
   | tionwit |    |                           |          |             |
   | h   SHA |    |                           |          |             |
   | -512    |    |                           |          |             |
   +---------+----+---------------------------+----------+-------------+


Appendix B.  Encryption Algorithm Identifier Cross-Reference

   This appendix contains a table cross-referencing the "alg"
   (algorithm) and "enc" (encryption method) values used in this
   specification with the equivalent identifiers used by other standards
   and software packages.  See XML Encryption
   [W3C.REC-xmlenc-core-20021210], XML Encryption 1.1
   [W3C.CR-xmlenc-core1-20120313], and Java Cryptography Architecture
   [JCA] for more information about the names defined by those
   documents.

   For the composite algorithms "A128CBC-HS256", "A192CBC-HS384", and
   "A256CBC-HS512", the corresponding AES CBC algorithm identifiers are
   listed.




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   +----------+--------+--------------------------+--------------------+
   | Algorith | JWE    | XML ENC                  | JCA                |
   | m        |        |                          |                    |
   +----------+--------+--------------------------+--------------------+
   | RSAES-PK | RSA1_5 | http://www.w3.org/2001/0 | RSA/ECB/PKCS1Paddi |
   | CS1-V1_5 |        | 4/xmlenc#rsa-1_5         | ng                 |
   | RSAES    | RSA-OA | http://www.w3.org/2001/0 | RSA/ECB/OAEPWithSH |
   | using    | EP     | 4/xmlenc#rsa-oaep-mgf1p  | A-1AndMGF1Padding  |
   | Optimal  |        |                          |                    |
   | Asymmetr |        |                          |                    |
   | ic       |        |                          |                    |
   |  Encrypt |        |                          |                    |
   | ion      |        |                          |                    |
   |   Paddin |        |                          |                    |
   | g (OAEP) |        |                          |                    |
   | Elliptic | ECDH-E | http://www.w3.org/2009/x |                    |
   | Curve    | S      | mlenc11#ECDH-ES          |                    |
   | Diffie-H |        |                          |                    |
   | ellman   |        |                          |                    |
   |  Ephemer |        |                          |                    |
   | alStatic |        |                          |                    |
   | Advanced | A128KW | http://www.w3.org/2001/0 |                    |
   | Encrypti |        | 4/xmlenc#kw-aes128       |                    |
   | on       |        |                          |                    |
   |  Standar |        |                          |                    |
   | d(AES)   |        |                          |                    |
   |  Key Wra |        |                          |                    |
   | pAlgorit |        |                          |                    |
   | hmusing  |        |                          |                    |
   |   128 bi |        |                          |                    |
   | t keys   |        |                          |                    |
   | AES Key  | A192KW | http://www.w3.org/2001/0 |                    |
   | Wrap     |        | 4/xmlenc#kw-aes192       |                    |
   | Algorith |        |                          |                    |
   | musing   |        |                          |                    |
   |  192 bit |        |                          |                    |
   |  keys    |        |                          |                    |
   | AES Key  | A256KW | http://www.w3.org/2001/0 |                    |
   | Wrap     |        | 4/xmlenc#kw-aes256       |                    |
   | Algorith |        |                          |                    |
   | musing   |        |                          |                    |
   |  256 bit |        |                          |                    |
   |  keys    |        |                          |                    |








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   | AES in   | A128CB | http://www.w3.org/2001/0 | AES/CBC/PKCS5Paddi |
   | Cipher   | C-HS25 | 4/xmlenc#aes128-cbc      | ng                 |
   | Block    | 6      |                          |                    |
   | Chaining |        |                          |                    |
   | (CBC)    |        |                          |                    |
   | mode     |        |                          |                    |
   | with     |        |                          |                    |
   | PKCS #5  |        |                          |                    |
   | padding  |        |                          |                    |
   | using    |        |                          |                    |
   | 128 bit  |        |                          |                    |
   | keys     |        |                          |                    |
   | AES in   | A192CB | http://www.w3.org/2001/0 | AES/CBC/PKCS5Paddi |
   | CBC mode | C-HS38 | 4/xmlenc#aes192-cbc      | ng                 |
   | with     | 4      |                          |                    |
   | PKCS #5  |        |                          |                    |
   | padding  |        |                          |                    |
   | using    |        |                          |                    |
   | 192 bit  |        |                          |                    |
   | keys     |        |                          |                    |
   | AES in   | A256CB | http://www.w3.org/2001/0 | AES/CBC/PKCS5Paddi |
   | CBC mode | C-HS51 | 4/xmlenc#aes256-cbc      | ng                 |
   | with     | 2      |                          |                    |
   | PKCS #5  |        |                          |                    |
   | padding  |        |                          |                    |
   | using    |        |                          |                    |
   | 256 bit  |        |                          |                    |
   | keys     |        |                          |                    |
   | AES in   | A128GC | http://www.w3.org/2009/x | AES/GCM/NoPadding  |
   | Galois/C | M      | mlenc11#aes128-gcm       |                    |
   | ounter   |        |                          |                    |
   |  Mode    |        |                          |                    |
   |  (GCM)   |        |                          |                    |
   |  using   |        |                          |                    |
   |  128 bit |        |                          |                    |
   |  keys    |        |                          |                    |
   | AES GCM  | A192GC | http://www.w3.org/2009/x | AES/GCM/NoPadding  |
   | using    | M      | mlenc11#aes192-gcm       |                    |
   | 192 bit  |        |                          |                    |
   | keys     |        |                          |                    |
   | AES GCM  | A256GC | http://www.w3.org/2009/x | AES/GCM/NoPadding  |
   | using    | M      | mlenc11#aes256-gcm       |                    |
   | 256 bit  |        |                          |                    |
   | keys     |        |                          |                    |
   +----------+--------+--------------------------+--------------------+






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Appendix C.  Test Cases for AES_CBC_HMAC_SHA2 Algorithms

   The following test cases can be used to validate implementations of
   the AES_CBC_HMAC_SHA2 algorithms defined in Section 4.10.  They are
   also intended to correspond to test cases that may appear in a future
   version of [I-D.mcgrew-aead-aes-cbc-hmac-sha2], demonstrating that
   the cryptographic computations performed are the same.

   The variable names are those defined in Section 4.10.  All values are
   hexadecimal.









































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C.1.  Test Cases for AES_128_CBC_HMAC_SHA_256

   AES_128_CBC_HMAC_SHA_256

     K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
               10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

     MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f

     ENC_KEY = 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

     P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
               6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
               69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
               74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
               65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
               6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
               20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
               75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

     IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

     A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
               69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
               4b 65 72 63 6b 68 6f 66 66 73

     AL =      00 00 00 00 00 00 01 50

     E =       c8 0e df a3 2d df 39 d5 ef 00 c0 b4 68 83 42 79
               a2 e4 6a 1b 80 49 f7 92 f7 6b fe 54 b9 03 a9 c9
               a9 4a c9 b4 7a d2 65 5c 5f 10 f9 ae f7 14 27 e2
               fc 6f 9b 3f 39 9a 22 14 89 f1 63 62 c7 03 23 36
               09 d4 5a c6 98 64 e3 32 1c f8 29 35 ac 40 96 c8
               6e 13 33 14 c5 40 19 e8 ca 79 80 df a4 b9 cf 1b
               38 4c 48 6f 3a 54 c5 10 78 15 8e e5 d7 9d e5 9f
               bd 34 d8 48 b3 d6 95 50 a6 76 46 34 44 27 ad e5
               4b 88 51 ff b5 98 f7 f8 00 74 b9 47 3c 82 e2 db

     M =       65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4
               e6 e5 45 82 47 65 15 f0 ad 9f 75 a2 b7 1c 73 ef

     T =       65 2c 3f a3 6b 0a 7c 5b 32 19 fa b3 a3 0b c1 c4









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C.2.  Test Cases for AES_192_CBC_HMAC_SHA_384

     K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
               10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
               20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f

     MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
               10 11 12 13 14 15 16 17

     ENC_KEY = 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27
               28 29 2a 2b 2c 2d 2e 2f

     P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
               6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
               69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
               74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
               65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
               6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
               20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
               75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

     IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

     A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
               69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
               4b 65 72 63 6b 68 6f 66 66 73

     AL =      00 00 00 00 00 00 01 50

     E =       ea 65 da 6b 59 e6 1e db 41 9b e6 2d 19 71 2a e5
               d3 03 ee b5 00 52 d0 df d6 69 7f 77 22 4c 8e db
               00 0d 27 9b dc 14 c1 07 26 54 bd 30 94 42 30 c6
               57 be d4 ca 0c 9f 4a 84 66 f2 2b 22 6d 17 46 21
               4b f8 cf c2 40 0a dd 9f 51 26 e4 79 66 3f c9 0b
               3b ed 78 7a 2f 0f fc bf 39 04 be 2a 64 1d 5c 21
               05 bf e5 91 ba e2 3b 1d 74 49 e5 32 ee f6 0a 9a
               c8 bb 6c 6b 01 d3 5d 49 78 7b cd 57 ef 48 49 27
               f2 80 ad c9 1a c0 c4 e7 9c 7b 11 ef c6 00 54 e3

     M =       84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
               75 16 80 39 cc c7 33 d7 45 94 f8 86 b3 fa af d4
               86 f2 5c 71 31 e3 28 1e 36 c7 a2 d1 30 af de 57

     T =       84 90 ac 0e 58 94 9b fe 51 87 5d 73 3f 93 ac 20
               75 16 80 39 cc c7 33 d7






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C.3.  Test Cases for AES_256_CBC_HMAC_SHA_512

     K =       00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
               10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f
               20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
               30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f

     MAC_KEY = 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f
               10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f

     ENC_KEY = 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f
               30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f

     P =       41 20 63 69 70 68 65 72 20 73 79 73 74 65 6d 20
               6d 75 73 74 20 6e 6f 74 20 62 65 20 72 65 71 75
               69 72 65 64 20 74 6f 20 62 65 20 73 65 63 72 65
               74 2c 20 61 6e 64 20 69 74 20 6d 75 73 74 20 62
               65 20 61 62 6c 65 20 74 6f 20 66 61 6c 6c 20 69
               6e 74 6f 20 74 68 65 20 68 61 6e 64 73 20 6f 66
               20 74 68 65 20 65 6e 65 6d 79 20 77 69 74 68 6f
               75 74 20 69 6e 63 6f 6e 76 65 6e 69 65 6e 63 65

     IV =      1a f3 8c 2d c2 b9 6f fd d8 66 94 09 23 41 bc 04

     A =       54 68 65 20 73 65 63 6f 6e 64 20 70 72 69 6e 63
               69 70 6c 65 20 6f 66 20 41 75 67 75 73 74 65 20
               4b 65 72 63 6b 68 6f 66 66 73

     AL =      00 00 00 00 00 00 01 50

     E =       4a ff aa ad b7 8c 31 c5 da 4b 1b 59 0d 10 ff bd
               3d d8 d5 d3 02 42 35 26 91 2d a0 37 ec bc c7 bd
               82 2c 30 1d d6 7c 37 3b cc b5 84 ad 3e 92 79 c2
               e6 d1 2a 13 74 b7 7f 07 75 53 df 82 94 10 44 6b
               36 eb d9 70 66 29 6a e6 42 7e a7 5c 2e 08 46 a1
               1a 09 cc f5 37 0d c8 0b fe cb ad 28 c7 3f 09 b3
               a3 b7 5e 66 2a 25 94 41 0a e4 96 b2 e2 e6 60 9e
               31 e6 e0 2c c8 37 f0 53 d2 1f 37 ff 4f 51 95 0b
               be 26 38 d0 9d d7 a4 93 09 30 80 6d 07 03 b1 f6

     M =       4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
               2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5
               fd 30 a5 65 c6 16 ff b2 f3 64 ba ec e6 8f c4 07
               53 bc fc 02 5d de 36 93 75 4a a1 f5 c3 37 3b 9c

     T =       4d d3 b4 c0 88 a7 f4 5c 21 68 39 64 5b 20 12 bf
               2e 62 69 a8 c5 6a 81 6d bc 1b 26 77 61 95 5b c5




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Appendix D.  Example ECDH-ES Key Agreement Computation

   This example uses ECDH-ES Key Agreement and the Concat KDF to derive
   the Content Encryption Key (CEK) in the manner described in
   Section 4.7.  In this example, the ECDH-ES Direct Key Agreement mode
   ("alg" value "ECDH-ES") is used to produce an agreed upon key for AES
   GCM with 128 bit keys ("enc" value "A128GCM").

   In this example, a sender Alice is encrypting content to a recipient
   Bob. The sender (Alice) generates an ephemeral key for the key
   agreement computation.  Alice's ephemeral key (in JWK format) used
   for the key agreement computation in this example (including the
   private part) is:

     {"kty":"EC",
      "crv":"P-256",
      "x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
      "y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps",
      "d":"0_NxaRPUMQoAJt50Gz8YiTr8gRTwyEaCumd-MToTmIo"
     }

   The recipient's (Bob's) key (in JWK format) used for the key
   agreement computation in this example (including the private part)
   is:

     {"kty":"EC",
      "crv":"P-256",
      "x":"weNJy2HscCSM6AEDTDg04biOvhFhyyWvOHQfeF_PxMQ",
      "y":"e8lnCO-AlStT-NJVX-crhB7QRYhiix03illJOVAOyck",
      "d":"VEmDZpDXXK8p8N0Cndsxs924q6nS1RXFASRl6BfUqdw"
     }

   Header parameter values used in this example are as follows.  In this
   example, the "apu" (agreement PartyUInfo) parameter value is the
   base64url encoding of the UTF-8 string "Alice" and the "apv"
   (agreement PartyVInfo) parameter value is the base64url encoding of
   the UTF-8 string "Bob".  The "epk" parameter is used to communicate
   the sender's (Alice's) ephemeral public key value to the recipient
   (Bob).












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     {"alg":"ECDH-ES",
      "enc":"A128GCM",
      "apu":"QWxpY2U",
      "apv":"Qm9i",
      "epk":
       {"kty":"EC",
        "crv":"P-256",
        "x":"gI0GAILBdu7T53akrFmMyGcsF3n5dO7MmwNBHKW5SV0",
        "y":"SLW_xSffzlPWrHEVI30DHM_4egVwt3NQqeUD7nMFpps"
       }
     }

   The resulting Concat KDF [NIST.800-56A] parameter values are:

   Z  This is set to the ECDH-ES key agreement output.  (This value is
      often not directly exposed by libraries, due to NIST security
      requirements, and only serves as an input to a KDF.)

   keydatalen  This value is 128 - the number of bits in the desired
      output key (because "A128GCM" uses a 128 bit key).

   AlgorithmID  This is set to the octets representing the UTF-8 string
      "A128GCM" - [65, 49, 50, 56, 71, 67, 77].

   PartyUInfo  This is set to the octets representing the 32 bit big
      endian value 5 - [0, 0, 0, 5] - the number of octets in the
      PartyUInfo content "Alice", followed, by the octets representing
      the UTF-8 string "Alice" - [65, 108, 105, 99, 101].

   PartyVInfo  This is set to the octets representing the 32 bit big
      endian value 3 - [0, 0, 0, 3] - the number of octets in the
      PartyUInfo content "Bob", followed, by the octets representing the
      UTF-8 string "Bob" - [66, 111, 98].

   SuppPubInfo  This is set to the octets representing the 32 bit big
      endian value 128 - [0, 0, 0, 128] - the keydatalen value.

   SuppPrivInfo  This is set to the empty octet sequence.

   The resulting derived key, represented as a base64url encoded value
   is:

     jSNmj9QK9ZGQJ2xg5_TJpA








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Appendix E.  Acknowledgements

   Solutions for signing and encrypting JSON content were previously
   explored by Magic Signatures [MagicSignatures], JSON Simple Sign
   [JSS], Canvas Applications [CanvasApp], JSON Simple Encryption [JSE],
   and JavaScript Message Security Format [I-D.rescorla-jsms], all of
   which influenced this draft.

   The Authenticated Encryption with AES-CBC and HMAC-SHA
   [I-D.mcgrew-aead-aes-cbc-hmac-sha2] specification, upon which the
   AES_CBC_HMAC_SHA2 algorithms are based, was written by David A.
   McGrew and Kenny Paterson.  The test cases for AES_CBC_HMAC_SHA2 are
   based upon those for [I-D.mcgrew-aead-aes-cbc-hmac-sha2] by John
   Foley.

   Matt Miller wrote Using JavaScript Object Notation (JSON) Web
   Encryption (JWE) for Protecting JSON Web Key (JWK) Objects
   [I-D.miller-jose-jwe-protected-jwk], which the password-based
   encryption content of this draft is based upon.

   This specification is the work of the JOSE Working Group, which
   includes dozens of active and dedicated participants.  In particular,
   the following individuals contributed ideas, feedback, and wording
   that influenced this specification:

   Dirk Balfanz, Richard Barnes, John Bradley, Brian Campbell, Breno de
   Medeiros, Yaron Y. Goland, Dick Hardt, Jeff Hodges, Edmund Jay, James
   Manger, Matt Miller, Tony Nadalin, Axel Nennker, John Panzer,
   Emmanuel Raviart, Nat Sakimura, Jim Schaad, Hannes Tschofenig, and
   Sean Turner.

   Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
   Sean Turner and Stephen Farrell served as Security area directors
   during the creation of this specification.


Appendix F.  Document History

   [[ to be removed by the RFC editor before publication as an RFC ]]

   -14

   o  Removed "PBKDF2" key type and added "p2s" and "p2c" header
      parameters for use with the PBES2 algorithms.

   o  Made the RSA private key parameters that are there to enable
      optimizations be RECOMMENDED rather than REQUIRED.




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   o  Added algorithm identifiers for AES algorithms using 192 bit keys
      and for RSASSA-PSS using HMAC SHA-384.

   o  Added security considerations about key lifetimes, addressing
      issue #18.

   o  Added an example ECDH-ES key agreement computation.

   -13

   o  Added key encryption with AES GCM as specified in
      draft-jones-jose-aes-gcm-key-wrap-01, addressing issue #13.

   o  Added security considerations text limiting the number of times
      that an AES GCM key can be used for key encryption or direct
      encryption, per Section 8.3 of NIST SP 800-38D, addressing issue
      #28.

   o  Added password-based key encryption as specified in
      draft-miller-jose-jwe-protected-jwk-02.

   -12

   o  In the Direct Key Agreement case, the Concat KDF AlgorithmID is
      set to the octets of the UTF-8 representation of the "enc" header
      parameter value.

   o  Restored the "apv" (agreement PartyVInfo) parameter.

   o  Moved the "epk", "apu", and "apv" Header Parameter definitions to
      be with the algorithm descriptions that use them.

   o  Changed terminology from "block encryption" to "content
      encryption".

   -11

   o  Removed the Encrypted Key value from the AAD computation since it
      is already effectively integrity protected by the encryption
      process.  The AAD value now only contains the representation of
      the JWE Encrypted Header.

   o  Removed "apv" (agreement PartyVInfo) since it is no longer used.

   o  Added more information about the use of PartyUInfo during key
      agreement.





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   o  Use the keydatalen as the SuppPubInfo value for the Concat KDF
      when doing key agreement, as RFC 2631 does.

   o  Added algorithm identifiers for RSASSA-PSS with SHA-256 and SHA-
      512.

   o  Added a Parameter Information Class value to the JSON Web Key
      Parameters registry, which registers whether the parameter conveys
      public or private information.

   -10

   o  Changed the JWE processing rules for multiple recipients so that a
      single AAD value contains the header parameters and encrypted key
      values for all the recipients, enabling AES GCM to be safely used
      for multiple recipients.

   -09

   o  Expanded the scope of the JWK parameters to include private and
      symmetric key representations, as specified by
      draft-jones-jose-json-private-and-symmetric-key-00.

   o  Changed term "JWS Secured Input" to "JWS Signing Input".

   o  Changed from using the term "byte" to "octet" when referring to 8
      bit values.

   o  Specified that AES Key Wrap uses the default initial value
      specified in Section 2.2.3.1 of RFC 3394.  This addressed issue
      #19.

   o  Added Key Management Mode definitions to terminology section and
      used the defined terms to provide clearer key management
      instructions.  This addressed issue #5.

   o  Replaced "A128CBC+HS256" and "A256CBC+HS512" with "A128CBC-HS256"
      and "A256CBC-HS512".  The new algorithms perform the same
      cryptographic computations as [I-D.mcgrew-aead-aes-cbc-hmac-sha2],
      but with the Initialization Vector and Authentication Tag values
      remaining separate from the Ciphertext value in the output
      representation.  Also deleted the header parameters "epu"
      (encryption PartyUInfo) and "epv" (encryption PartyVInfo), since
      they are no longer used.

   o  Changed from using the term "Integrity Value" to "Authentication
      Tag".




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   -08

   o  Changed the name of the JWK key type parameter from "alg" to
      "kty".

   o  Replaced uses of the term "AEAD" with "Authenticated Encryption",
      since the term AEAD in the RFC 5116 sense implied the use of a
      particular data representation, rather than just referring to the
      class of algorithms that perform authenticated encryption with
      associated data.

   o  Applied editorial improvements suggested by Jeff Hodges.  Many of
      these simplified the terminology used.

   o  Added seriesInfo information to Internet Draft references.

   -07

   o  Added a data length prefix to PartyUInfo and PartyVInfo values.

   o  Changed the name of the JWK RSA modulus parameter from "mod" to
      "n" and the name of the JWK RSA exponent parameter from "xpo" to
      "e", so that the identifiers are the same as those used in RFC
      3447.

   o  Made several local editorial changes to clean up loose ends left
      over from to the decision to only support block encryption methods
      providing integrity.

   -06

   o  Removed the "int" and "kdf" parameters and defined the new
      composite Authenticated Encryption algorithms "A128CBC+HS256" and
      "A256CBC+HS512" to replace the former uses of AES CBC, which
      required the use of separate integrity and key derivation
      functions.

   o  Included additional values in the Concat KDF calculation -- the
      desired output size and the algorithm value, and optionally
      PartyUInfo and PartyVInfo values.  Added the optional header
      parameters "apu" (agreement PartyUInfo), "apv" (agreement
      PartyVInfo), "epu" (encryption PartyUInfo), and "epv" (encryption
      PartyVInfo).

   o  Changed the name of the JWK RSA exponent parameter from "exp" to
      "xpo" so as to allow the potential use of the name "exp" for a
      future extension that might define an expiration parameter for
      keys.  (The "exp" name is already used for this purpose in the JWT



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      specification.)

   o  Applied changes made by the RFC Editor to RFC 6749's registry
      language to this specification.

   -05

   o  Support both direct encryption using a shared or agreed upon
      symmetric key, and the use of a shared or agreed upon symmetric
      key to key wrap the CMK.  Specifically, added the "alg" values
      "dir", "ECDH-ES+A128KW", and "ECDH-ES+A256KW" to finish filling in
      this set of capabilities.

   o  Updated open issues.

   -04

   o  Added text requiring that any leading zero bytes be retained in
      base64url encoded key value representations for fixed-length
      values.

   o  Added this language to Registration Templates: "This name is case
      sensitive.  Names that match other registered names in a case
      insensitive manner SHOULD NOT be accepted."

   o  Described additional open issues.

   o  Applied editorial suggestions.

   -03

   o  Always use a 128 bit "authentication tag" size for AES GCM,
      regardless of the key size.

   o  Specified that use of a 128 bit IV is REQUIRED with AES CBC.  It
      was previously RECOMMENDED.

   o  Removed key size language for ECDSA algorithms, since the key size
      is implied by the algorithm being used.

   o  Stated that the "int" key size must be the same as the hash output
      size (and not larger, as was previously allowed) so that its size
      is defined for key generation purposes.

   o  Added the "kdf" (key derivation function) header parameter to
      provide crypto agility for key derivation.  The default KDF
      remains the Concat KDF with the SHA-256 digest function.




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   o  Clarified that the "mod" and "exp" values are unsigned.

   o  Added Implementation Requirements columns to algorithm tables and
      Implementation Requirements entries to algorithm registries.

   o  Changed AES Key Wrap to RECOMMENDED.

   o  Moved registries JSON Web Signature and Encryption Header
      Parameters and JSON Web Signature and Encryption Type Values to
      the JWS specification.

   o  Moved JSON Web Key Parameters registry to the JWK specification.

   o  Changed registration requirements from RFC Required to
      Specification Required with Expert Review.

   o  Added Registration Template sections for defined registries.

   o  Added Registry Contents sections to populate registry values.

   o  No longer say "the UTF-8 representation of the JWS Secured Input
      (which is the same as the ASCII representation)".  Just call it
      "the ASCII representation of the JWS Secured Input".

   o  Added "Collision Resistant Namespace" to the terminology section.

   o  Numerous editorial improvements.

   -02

   o  For AES GCM, use the "additional authenticated data" parameter to
      provide integrity for the header, encrypted key, and ciphertext
      and use the resulting "authentication tag" value as the JWE
      Authentication Tag.

   o  Defined minimum required key sizes for algorithms without
      specified key sizes.

   o  Defined KDF output key sizes.

   o  Specified the use of PKCS #5 padding with AES CBC.

   o  Generalized text to allow key agreement to be employed as an
      alternative to key wrapping or key encryption.

   o  Clarified that ECDH-ES is a key agreement algorithm.





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   o  Required implementation of AES-128-KW and AES-256-KW.

   o  Removed the use of "A128GCM" and "A256GCM" for key wrapping.

   o  Removed "A512KW" since it turns out that it's not a standard
      algorithm.

   o  Clarified the relationship between "typ" header parameter values
      and MIME types.

   o  Generalized language to refer to Message Authentication Codes
      (MACs) rather than Hash-based Message Authentication Codes (HMACs)
      unless in a context specific to HMAC algorithms.

   o  Established registries: JSON Web Signature and Encryption Header
      Parameters, JSON Web Signature and Encryption Algorithms, JSON Web
      Signature and Encryption "typ" Values, JSON Web Key Parameters,
      and JSON Web Key Algorithm Families.

   o  Moved algorithm-specific definitions from JWK to JWA.

   o  Reformatted to give each member definition its own section
      heading.

   -01

   o  Moved definition of "alg":"none" for JWSs here from the JWT
      specification since this functionality is likely to be useful in
      more contexts that just for JWTs.

   o  Added Advanced Encryption Standard (AES) Key Wrap Algorithm using
      512 bit keys ("A512KW").

   o  Added text "Alternatively, the Encoded JWS Signature MAY be
      base64url decoded to produce the JWS Signature and this value can
      be compared with the computed HMAC value, as this comparison
      produces the same result as comparing the encoded values".

   o  Corrected the Magic Signatures reference.

   o  Made other editorial improvements suggested by JOSE working group
      participants.

   -00

   o  Created the initial IETF draft based upon
      draft-jones-json-web-signature-04 and
      draft-jones-json-web-encryption-02 with no normative changes.



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   o  Changed terminology to no longer call both digital signatures and
      HMACs "signatures".


Author's Address

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/








































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