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JOSE Working Group                                              M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                            May 12, 2012
Expires: November 13, 2012


                       JSON Web Algorithms (JWA)
                 draft-ietf-jose-json-web-algorithms-02

Abstract

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

Requirements Language

   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 RFC 2119 [RFC2119].

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on November 13, 2012.

Copyright Notice

   Copyright (c) 2012 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
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect



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   to this document.  Code Components extracted from this document must
   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.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Cryptographic Algorithms for JWS . . . . . . . . . . . . . . .  4
     3.1.  "alg" (Algorithm) Header Parameter Values for JWS  . . . .  4
     3.2.  MAC with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512 . . .  5
     3.3.  Digital Signature with RSA SHA-256, RSA SHA-384, or
           RSA SHA-512  . . . . . . . . . . . . . . . . . . . . . . .  6
     3.4.  Digital Signature with ECDSA P-256 SHA-256, ECDSA
           P-384 SHA-384, or ECDSA P-521 SHA-512  . . . . . . . . . .  7
     3.5.  Creating a Plaintext JWS . . . . . . . . . . . . . . . . .  9
     3.6.  Additional Digital Signature/MAC Algorithms and
           Parameters . . . . . . . . . . . . . . . . . . . . . . . .  9
   4.  Cryptographic Algorithms for JWE . . . . . . . . . . . . . . .  9
     4.1.  "alg" (Algorithm) Header Parameter Values for JWE  . . . .  9
     4.2.  "enc" (Encryption Method) Header Parameter Values for
           JWE  . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     4.3.  "int" (Integrity Algorithm) Header Parameter Values
           for JWE  . . . . . . . . . . . . . . . . . . . . . . . . . 11
     4.4.  Key Encryption with RSA using RSA-PKCS1-1.5 Padding  . . . 11
     4.5.  Key Encryption with RSA using Optimal Asymmetric
           Encryption Padding (OAEP)  . . . . . . . . . . . . . . . . 11
     4.6.  Key Agreement with Elliptic Curve Diffie-Hellman
           Ephemeral Static (ECDH-ES) . . . . . . . . . . . . . . . . 12
     4.7.  Key Encryption with AES Key Wrap . . . . . . . . . . . . . 12
     4.8.  Plaintext Encryption with AES Cipher Block Chaining
           (CBC) Mode . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.9.  Plaintext Encryption with AES Galois/Counter Mode (GCM)  . 12
     4.10. Integrity Calculation with HMAC SHA-256, HMAC SHA-384,
           or HMAC SHA-512  . . . . . . . . . . . . . . . . . . . . . 13
     4.11. Additional Encryption Algorithms and Parameters  . . . . . 13
   5.  Cryptographic Algorithms for JWK . . . . . . . . . . . . . . . 13
     5.1.  "alg" (Algorithm Family) Parameter Values for JWK  . . . . 14
     5.2.  JWK Parameters for Elliptic Curve Keys . . . . . . . . . . 14
       5.2.1.  "crv" (Curve) Parameter  . . . . . . . . . . . . . . . 14
       5.2.2.  "x" (X Coordinate) Parameter . . . . . . . . . . . . . 14
       5.2.3.  "y" (Y Coordinate) Parameter . . . . . . . . . . . . . 14
     5.3.  JWK Parameters for RSA Keys  . . . . . . . . . . . . . . . 14
       5.3.1.  "mod" (Modulus) Parameter  . . . . . . . . . . . . . . 15
       5.3.2.  "exp" (Exponent) Parameter . . . . . . . . . . . . . . 15
     5.4.  Additional Key Algorithm Families and Parameters . . . . . 15



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   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
     6.1.  JSON Web Signature and Encryption Header Parameters
           Registry . . . . . . . . . . . . . . . . . . . . . . . . . 15
     6.2.  JSON Web Signature and Encryption Algorithms Registry  . . 15
     6.3.  JSON Web Signature and Encryption "typ" Values Registry  . 16
     6.4.  JSON Web Key Parameters Registry . . . . . . . . . . . . . 16
     6.5.  JSON Web Key Algorithm Families Registry . . . . . . . . . 16
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  Open Issues and Things To Be Done (TBD)  . . . . . . . . . . . 17
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 17
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 18
   Appendix A.  Digital Signature/MAC Algorithm Identifier
                Cross-Reference . . . . . . . . . . . . . . . . . . . 19
   Appendix B.  Encryption Algorithm Identifier Cross-Reference . . . 21
   Appendix C.  Acknowledgements  . . . . . . . . . . . . . . . . . . 25
   Appendix D.  Document History  . . . . . . . . . . . . . . . . . . 25
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 26

































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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] and JSON Web Encryption (JWE) [JWE] specifications.
   Enumerating the algorithms and identifiers for them in this
   specification, rather than in the JWS and JWE 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.  This specification also describes the semantics and
   operations that are specific to these algorithms and algorithm
   families.


2.  Terminology

   This specification uses the terminology defined by the JSON Web
   Signature (JWS) [JWS] and JSON Web Encryption (JWE) [JWE]
   specifications.


3.  Cryptographic Algorithms for JWS

   JWS uses cryptographic algorithms to digitally sign or MAC 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:

   +--------------------+----------------------------------------------+
   | alg Parameter      | Digital Signature or MAC Algorithm           |
   | Value              |                                              |
   +--------------------+----------------------------------------------+
   | HS256              | HMAC using SHA-256 hash algorithm            |
   | HS384              | HMAC using SHA-384 hash algorithm            |
   | HS512              | HMAC using SHA-512 hash algorithm            |
   | RS256              | RSA using SHA-256 hash algorithm             |
   | RS384              | RSA using SHA-384 hash algorithm             |
   | RS512              | RSA using SHA-512 hash algorithm             |
   | ES256              | ECDSA using P-256 curve and SHA-256 hash     |
   |                    | algorithm                                    |
   | ES384              | ECDSA using P-384 curve and SHA-384 hash     |
   |                    | algorithm                                    |




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   | ES512              | ECDSA using P-521 curve and SHA-512 hash     |
   |                    | algorithm                                    |
   | none               | No digital signature or MAC value included   |
   +--------------------+----------------------------------------------+

   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.

   Of these algorithms, only HMAC SHA-256 and "none" MUST be implemented
   by conforming JWS implementations.  It is RECOMMENDED that
   implementations also support the RSA SHA-256 and ECDSA P-256 SHA-256
   algorithms.  Support for other algorithms and key sizes is OPTIONAL.

3.2.  MAC with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512

   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 Secured 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 cryptographic hash functions as
   defined in FIPS 180-3 [FIPS.180-3].  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 as follows:

   1.  Apply the HMAC SHA-256 algorithm to the bytes of the UTF-8
       representation of the JWS Secured Input (which is the same as the
       ASCII representation) using the shared key to produce an HMAC
       value.

   2.  Base64url encode the resulting HMAC value.

   The output is the Encoded JWS Signature for that JWS.

   The HMAC SHA-256 MAC for a JWS is validated as follows:




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   1.  Apply the HMAC SHA-256 algorithm to the bytes of the UTF-8
       representation of the JWS Secured Input (which is the same as the
       ASCII representation) of the JWS using the shared key.

   2.  Base64url encode the resulting HMAC value.

   3.  If the Encoded JWS Signature and the base64url encoded HMAC value
       exactly match, then one has confirmation that the shared key was
       used to generate the HMAC on the JWS and that the contents of the
       JWS have not be tampered with.

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

   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.

   Securing content with the HMAC SHA-384 and HMAC SHA-512 algorithms is
   performed identically to the procedure for HMAC SHA-256 - just with
   correspondingly larger minimum key sizes and result values.

3.3.  Digital Signature with RSA SHA-256, RSA SHA-384, or RSA SHA-512

   This section defines the use of the RSASSA-PKCS1-v1_5 digital
   signature algorithm as defined in RFC 3447 [RFC3447], Section 8.2
   (commonly known as PKCS#1), using SHA-256, SHA-384, or SHA-512 as the
   hash function.  The RSASSA-PKCS1-v1_5 algorithm is described in FIPS
   186-3 [FIPS.186-3], Section 5.5, and the SHA-256, SHA-384, and SHA-
   512 cryptographic hash functions are defined in FIPS 180-3
   [FIPS.180-3].  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 RSA digital
   signature using the respective hash function.

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

   Note that while Section 8 of RFC 3447 [RFC3447] explicitly calls for
   people not to adopt RSASSA-PKCS1 for new applications and instead
   requests that people transition to RSASSA-PSS, for interoperability
   reasons, this specification does use RSASSA-PKCS1 because it commonly
   implemented.

   The RSA SHA-256 digital signature is generated as follows:

   1.  Generate a digital signature of the bytes of the UTF-8
       representation of the JWS Secured Input (which is the same as the
       ASCII representation) using RSASSA-PKCS1-V1_5-SIGN and the SHA-



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       256 hash function with the desired private key.  The output will
       be a byte array.

   2.  Base64url encode the resulting byte array.

   The output is the Encoded JWS Signature for that JWS.

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

   1.  Take the Encoded JWS Signature and base64url decode it into a
       byte array.  If decoding fails, the JWS MUST be rejected.

   2.  Submit the bytes of the UTF-8 representation of the JWS Secured
       Input (which is the same as the ASCII representation) 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 RSA SHA-384 and RSA SHA-512 algorithms is performed
   identically to the procedure for RSA SHA-256 - just with
   correspondingly larger result values.

3.4.  Digital Signature with ECDSA P-256 SHA-256, ECDSA P-384 SHA-384,
      or ECDSA P-521 SHA-512

   The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined by
   FIPS 186-3 [FIPS.186-3].  ECDSA 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 also
   defined in FIPS 186-3.  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.

   A key of size 160 bits or larger MUST be used with these algorithms.

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



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   1.  Generate a digital signature of the bytes of the UTF-8
       representation of the JWS Secured Input (which is the same as the
       ASCII representation) using ECDSA P-256 SHA-256 with the desired
       private key.  The output will be the EC point (R, S), where R and
       S are unsigned integers.

   2.  Turn R and S into byte arrays in big endian order.  Each array
       will be 32 bytes long.

   3.  Concatenate the two byte arrays in the order R and then S.

   4.  Base64url encode the resulting 64 byte array.

   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 a
       byte array.  If decoding fails, the JWS MUST be rejected.

   2.  The output of the base64url decoding MUST be a 64 byte array.

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

   4.  Submit the bytes of the UTF-8 representation of the JWS Secured
       Input (which is the same as the ASCII representation), 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.

   The ECDSA validator will then determine if the digital signature is
   valid, given the inputs.  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.
   The consequence of this is that one must validate an ECDSA digital
   signature by submitting the previously specified inputs to an ECDSA
   validator.

   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 with correspondingly larger result values.





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3.5.  Creating a Plaintext JWS

   To support use cases where the content is secured by a means other
   than a digital signature or MAC value, JWSs MAY also be created
   without them.  These are called "Plaintext JWSs".  Plaintext JWSs
   MUST use the "alg" value "none", and are formatted identically to
   other JWSs, but with an empty JWS Signature value.

3.6.  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 defined in
   the IANA JSON Web Signature and Encryption Algorithms registry
   Section 6.2 or be a URI 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
   "alg" value space.  The values used by the two specifications MUST be
   distinct, as the "alg" value MAY be used to determine whether the
   object is a JWS or JWE.

   Likewise, additional reserved header parameter names MAY be defined
   via the IANA JSON Web Signature and Encryption Header Parameters
   registry Section 6.1.  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 Master Key
   (CMK) 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 CMK, producing the JWE
   Encrypted Key, or to use key agreement to agree upon the CMK.






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   +-----------+-------------------------------------------------------+
   | alg       | Key Encryption or Agreement Algorithm                 |
   | Parameter |                                                       |
   | Value     |                                                       |
   +-----------+-------------------------------------------------------+
   | RSA1_5    | RSA using RSA-PKCS1-1.5 padding, as defined in RFC    |
   |           | 3447 [RFC3447]                                        |
   | RSA-OAEP  | RSA using Optimal Asymmetric Encryption Padding       |
   |           | (OAEP), as defined in RFC 3447 [RFC3447]              |
   | ECDH-ES   | Elliptic Curve Diffie-Hellman Ephemeral Static, as    |
   |           | defined in RFC 6090 [RFC6090], and using the Concat   |
   |           | KDF, as defined in Section 5.8.1 of [NIST.800-56A],   |
   |           | where the Digest Method is SHA-256 and all OtherInfo  |
   |           | parameters are the empty bit string                   |
   | A128KW    | Advanced Encryption Standard (AES) Key Wrap Algorithm |
   |           | using 128 bit keys, as defined in RFC 3394 [RFC3394]  |
   | A256KW    | Advanced Encryption Standard (AES) Key Wrap Algorithm |
   |           | using 256 bit keys, as defined in RFC 3394 [RFC3394]  |
   +-----------+-------------------------------------------------------+

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.

   +-----------+-------------------------------------------------------+
   | enc       | Block Encryption Algorithm                            |
   | Parameter |                                                       |
   | Value     |                                                       |
   +-----------+-------------------------------------------------------+
   | A128CBC   | Advanced Encryption Standard (AES) using 128 bit keys |
   |           | in Cipher Block Chaining (CBC) mode using PKCS #5     |
   |           | padding, as defined in [FIPS.197] and [NIST.800-38A]  |
   | A256CBC   | Advanced Encryption Standard (AES) using 256 bit keys |
   |           | in Cipher Block Chaining (CBC) mode using PKCS #5     |
   |           | padding, as defined in [FIPS.197] and [NIST.800-38A]  |
   | A128GCM   | Advanced Encryption Standard (AES) using 128 bit keys |
   |           | in Galois/Counter Mode (GCM), as defined in           |
   |           | [FIPS.197] and [NIST.800-38D]                         |
   | A256GCM   | Advanced Encryption Standard (AES) using 256 bit keys |
   |           | in Galois/Counter Mode (GCM), as defined in           |
   |           | [FIPS.197] and [NIST.800-38D]                         |
   +-----------+-------------------------------------------------------+

   See Appendix B for a table cross-referencing the encryption "alg"
   (algorithm) and "enc" (encryption method) values used in this



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   specification with the equivalent identifiers used by other standards
   and software packages.

   Of these "alg" and "enc" algorithms, only RSA-PKCS1-1.5 with 2048 bit
   keys, AES-128-KW, AES-256-KW, AES-128-CBC, and AES-256-CBC MUST be
   implemented by conforming JWE implementations.  It is RECOMMENDED
   that implementations also support ECDH-ES with 256 bit keys, AES-128-
   GCM, and AES-256-GCM.  Support for other algorithms and key sizes is
   OPTIONAL.

4.3.  "int" (Integrity Algorithm) Header Parameter Values for JWE

   The table below is the set of "int" (integrity algorithm) header
   parameter values defined by this specification for use with JWE.
   Note that these are the HMAC SHA subset of the "alg" (algorithm)
   header parameter values defined for use with JWS Section 3.1. />

        +---------------------+-----------------------------------+
        | int Parameter Value | Algorithm                         |
        +---------------------+-----------------------------------+
        | HS256               | HMAC using SHA-256 hash algorithm |
        | HS384               | HMAC using SHA-384 hash algorithm |
        | HS512               | HMAC using SHA-512 hash algorithm |
        +---------------------+-----------------------------------+

   Of these "int" algorithms, only HMAC SHA-256 MUST be implemented by
   conforming JWE implementations.  It is RECOMMENDED that
   implementations also support the RSA SHA-256 and ECDSA P-256 SHA-256
   algorithms.

4.4.  Key Encryption with RSA using RSA-PKCS1-1.5 Padding

   This section defines the specifics of encrypting a JWE CMK with RSA
   using RSA-PKCS1-1.5 padding, as defined in RFC 3447 [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.

4.5.  Key Encryption with RSA using Optimal Asymmetric Encryption
      Padding (OAEP)

   This section defines the specifics of encrypting a JWE CMK with RSA
   using Optimal Asymmetric Encryption Padding (OAEP), as defined in RFC
   3447 [RFC3447].  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.




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

   This section defines the specifics of agreeing upon a JWE CMK with
   Elliptic Curve Diffie-Hellman Ephemeral Static, as defined in RFC
   6090 [RFC6090], and using the Concat KDF, as defined in Section 5.8.1
   of [NIST.800-56A], where the Digest Method is SHA-256 and all
   OtherInfo parameters are the empty bit string.  The "alg" header
   parameter value "ECDH-ES" is used in this case.

   A key of size 160 bits or larger MUST be used for the Elliptic Curve
   keys used with this algorithm.  The output of the Concat KDF MUST be
   a key of the same length as that used by the "enc" algorithm.

   An "epk" (ephemeral public key) value MUST only be used for a single
   key agreement transaction.

4.7.  Key Encryption with AES Key Wrap

   This section defines the specifics of encrypting a JWE CMK with the
   Advanced Encryption Standard (AES) Key Wrap Algorithm using 128 or
   256 bit keys, as defined in RFC 3394 [RFC3394].  The "alg" header
   parameter values "A128KW" or "A256KW" are used in this case.

4.8.  Plaintext Encryption with AES Cipher Block Chaining (CBC) Mode

   This section defines the specifics of encrypting the JWE Plaintext
   with Advanced Encryption Standard (AES) in Cipher Block Chaining
   (CBC) mode using PKCS #5 padding using 128 or 256 bit keys, as
   defined in [FIPS.197] and [NIST.800-38A].  The "enc" header parameter
   values "A128CBC" or "A256CBC" are used in this case.

   Use of an Initialization Vector (IV) of size 128 bits is RECOMMENDED
   with this algorithm.

4.9.  Plaintext Encryption with AES Galois/Counter Mode (GCM)

   This section defines the specifics of encrypting the JWE Plaintext
   with Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM)
   using 128 or 256 bit keys, as defined in [FIPS.197] and
   [NIST.800-38D].  The "enc" header parameter values "A128GCM" or
   "A256GCM" are used in this case.

   Use of an Initialization Vector (IV) of size 96 bits is REQUIRED with
   this algorithm.

   The "additional authenticated data" parameter value for the
   encryption is the concatenation of the Encoded JWE Header, a period



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   ('.') character, and the Encoded JWE Encrypted Key.

   The requested size of the "authentication tag" output MUST be the
   same as the key size (for instance, 128 bits for "A128GCM").

   As GCM is an AEAD algorithm, the JWE Integrity Value is set to be the
   "authentication tag" value produced by the encryption.

4.10.  Integrity Calculation with HMAC SHA-256, HMAC SHA-384, or HMAC
       SHA-512

   This section defines the specifics of computing a JWE Integrity Value
   with HMAC SHA-256, HMAC SHA-384, or HMAC SHA-512 as defined in FIPS
   180-3 [FIPS.180-3].  The "int" header parameter values "HS256",
   "HS384", or "HS512" are used in this case.

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

4.11.  Additional Encryption Algorithms and Parameters

   Additional algorithms MAY be used to protect JWEs with corresponding
   "alg" (algorithm), "enc" (encryption method), and "int" (integrity
   algorithm) header parameter values being defined to refer to them.
   New "alg", "enc", and "int" header parameter values SHOULD either be
   defined in the IANA JSON Web Signature and Encryption Algorithms
   registry Section 6.2 or be a URI 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", "enc", and "int" 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 MAY be used to determine whether the
   object is a JWS or JWE.

   Likewise, additional reserved header parameter names MAY be defined
   via the IANA JSON Web Signature and Encryption Header Parameters
   registry Section 6.1.  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.


5.  Cryptographic Algorithms for JWK

   A JSON Web Key (JWK) [JWK] is a JSON data structure that represents a



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   public 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
   algorithm families to be used for those public keys and the algorithm
   family specific parameters for representing those keys.

5.1.  "alg" (Algorithm Family) Parameter Values for JWK

   The table below is the set of "alg" (algorithm family) parameter
   values that are defined by this specification for use in JWKs.

     +---------------------+----------------------------------------+
     | alg Parameter Value | Algorithm Family                       |
     +---------------------+----------------------------------------+
     | EC                  | Elliptic Curve [FIPS.186-3] key family |
     | RSA                 | RSA [RFC3447] key family               |
     +---------------------+----------------------------------------+

5.2.  JWK Parameters for Elliptic Curve Keys

   JWKs can represent Elliptic Curve [FIPS.186-3] keys.  In this case,
   the "alg" member value MUST be "EC".  Furthermore, these additional
   members MUST be present:

5.2.1.  "crv" (Curve) Parameter

   The "crv" (curve) member identifies the cryptographic curve used with
   the key.  Values defined by this specification are "P-256", "P-384"
   and "P-521".  Additional "crv" values MAY be used, provided they are
   understood by implementations using that Elliptic Curve key.  The
   "crv" value is case sensitive.  Its value MUST be a string.

5.2.2.  "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.

5.2.3.  "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.

5.3.  JWK Parameters for RSA Keys

   JWKs can represent RSA [RFC3447] keys.  In this case, the "alg"
   member value MUST be "RSA".  Furthermore, these additional members
   MUST be present:



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5.3.1.  "mod" (Modulus) Parameter

   The "mod" (modulus) member contains the modulus value for the RSA
   public key.  It is represented as the base64url encoding of the
   value's big endian representation.

5.3.2.  "exp" (Exponent) Parameter

   The "exp" (exponent) member contains the exponent value for the RSA
   public key.  It is represented as the base64url encoding of the
   value's big endian representation.

5.4.  Additional Key Algorithm Families and Parameters

   Public keys using additional algorithm families MAY be represented
   using JWK data structures with corresponding "alg" (algorithm family)
   parameter values being defined to refer to them.  New "alg" parameter
   values SHOULD either be defined in the IANA JSON Web Key Algorithm
   Families registry Section 6.5 or be a URI that contains a collision
   resistant namespace.

   Likewise, parameters for representing keys for additional algorithm
   families or additional key properties SHOULD either be defined in the
   IANA JSON Web Key Parameters registry Section 6.4 or be a URI that
   contains a collision resistant namespace.


6.  IANA Considerations

6.1.  JSON Web Signature and Encryption Header Parameters Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption Header Parameters registry for reserved JWS and JWE header
   parameter names.  Inclusion in the registry is RFC Required in the
   RFC 5226 [RFC5226] sense.  The registry records the reserved header
   parameter name and a reference to the RFC that defines it.  This
   specification registers the header parameter names defined in JSON
   Web Signature (JWS) [JWS], Section 4.1 and JSON Web Encryption (JWE)
   [JWE], Section 4.1.

6.2.  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), "enc" (encryption method), and "int" (integrity
   algorithm) header parameters.  Inclusion in the registry is RFC
   Required in the RFC 5226 [RFC5226] sense.  The registry records the
   algorithm usage "alg", "enc", or "int", the value, and a pointer to



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   the RFC that defines it.  This specification registers the values
   defined in Section 3.1, Section 4.1, Section 4.2, and Section 4.3.

6.3.  JSON Web Signature and Encryption "typ" Values Registry

   This specification establishes the IANA JSON Web Signature and
   Encryption "typ" Values registry for values of the JWS and JWE "typ"
   (type) header parameter.  Inclusion in the registry is RFC Required
   in the RFC 5226 [RFC5226] sense.  It is RECOMMENDED that all
   registered "typ" values also register a MIME Media Type RFC 2045
   [RFC2045] that the registered value is a short name for.  The
   registry records the "typ" value, the MIME type value that it is an
   abbreviation for (if any), and a pointer to the RFC that defines it.

   MIME Media Type RFC 2045 [RFC2045] values MUST NOT be directly
   registered as new "typ" values; rather, new "typ" values MAY be
   registered as short names for MIME types.

6.4.  JSON Web Key Parameters Registry

   This specification establishes the IANA JSON Web Key Parameters
   registry for reserved JWK parameter names.  Inclusion in the registry
   is RFC Required in the RFC 5226 [RFC5226] sense.  The registry
   records the reserved parameter name and a reference to the RFC that
   defines it.  This specification registers the parameter names defined
   in JSON Web Key (JWK) [JWK], Section 4.2, JSON Web Encryption (JWE)
   [JWE], Section 4.1, Section 5.2, and Section 5.3.

6.5.  JSON Web Key Algorithm Families Registry

   This specification establishes the IANA JSON Web Key Algorithm
   Families registry for values of the JWK "alg" (algorithm family)
   parameter.  Inclusion in the registry is RFC Required in the RFC 5226
   [RFC5226] sense.  The registry records the "alg" value and a pointer
   to the RFC that defines it.  This specification registers the values
   defined in Section 5.1.


7.  Security Considerations

   The security considerations in the JWS, JWE, and JWK specifications
   also 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.




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8.  Open Issues and Things To Be Done (TBD)

   The following items remain to be done in this draft:

   o  Find values for encryption algorithm cross-reference table
      currently listed as "TBD" or determine that they do not exist.


9.  References

9.1.  Normative References

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

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

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

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", May 2012.

   [JWK]      Jones, M., "JSON Web Key (JWK)", May 2012.

   [JWS]      Jones, M., Bradley, J., and N. Sakimura, "JSON Web
              Signature (JWS)", May 2012.

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

   [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 (Revised)", NIST PUB



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              800-56A, March 2007.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [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.

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

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

   [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
              Curve Cryptography Algorithms", RFC 6090, February 2011.

9.2.  Informative References

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

   [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.



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

   [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.

   +-------+-----+----------------------------+----------+-------------+
   | Algor | JWS | XML DSIG                   | JCA      | OID         |
   | ithm  |     |                            |          |             |
   +-------+-----+----------------------------+----------+-------------+
   | HMAC  | HS2 | http://www.w3.org/2001/04/ | HmacSHA2 | 1.2.840.113 |
   | using | 56  | xmldsig-more#hmac-sha256   | 56       | 549.2.9     |
   | SHA-2 |     |                            |          |             |
   | 56    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |





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   | HMAC  | HS3 | http://www.w3.org/2001/04/ | HmacSHA3 | 1.2.840.113 |
   | using | 84  | xmldsig-more#hmac-sha384   | 84       | 549.2.10    |
   | SHA-3 |     |                            |          |             |
   | 84    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | HMAC  | HS5 | http://www.w3.org/2001/04/ | HmacSHA5 | 1.2.840.113 |
   | using | 12  | xmldsig-more#hmac-sha512   | 12       | 549.2.11    |
   | SHA-5 |     |                            |          |             |
   | 12    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | RSA   | RS2 | http://www.w3.org/2001/04/ | SHA256wi | 1.2.840.113 |
   | using | 56  | xmldsig-more#rsa-sha256    | thRSA    | 549.1.1.11  |
   | SHA-2 |     |                            |          |             |
   | 56    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | RSA   | RS3 | http://www.w3.org/2001/04/ | SHA384wi | 1.2.840.113 |
   | using | 84  | xmldsig-more#rsa-sha384    | thRSA    | 549.1.1.12  |
   | SHA-3 |     |                            |          |             |
   | 84    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | RSA   | RS5 | http://www.w3.org/2001/04/ | SHA512wi | 1.2.840.113 |
   | using | 12  | xmldsig-more#rsa-sha512    | thRSA    | 549.1.1.13  |
   | SHA-5 |     |                            |          |             |
   | 12    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | ECDSA | ES2 | http://www.w3.org/2001/04/ | SHA256wi | 1.2.840.100 |
   | using | 56  | xmldsig-more#ecdsa-sha256  | thECDSA  | 45.4.3.2    |
   | P-256 |     |                            |          |             |
   | curve |     |                            |          |             |
   | and   |     |                            |          |             |
   | SHA-2 |     |                            |          |             |
   | 56    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |






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   | ECDSA | ES3 | http://www.w3.org/2001/04/ | SHA384wi | 1.2.840.100 |
   | using | 84  | xmldsig-more#ecdsa-sha384  | thECDSA  | 45.4.3.3    |
   | P-384 |     |                            |          |             |
   | curve |     |                            |          |             |
   | and   |     |                            |          |             |
   | SHA-3 |     |                            |          |             |
   | 84    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   | ECDSA | ES5 | http://www.w3.org/2001/04/ | SHA512wi | 1.2.840.100 |
   | using | 12  | xmldsig-more#ecdsa-sha512  | thECDSA  | 45.4.3.4    |
   | P-521 |     |                            |          |             |
   | curve |     |                            |          |             |
   | and   |     |                            |          |             |
   | SHA-5 |     |                            |          |             |
   | 12    |     |                            |          |             |
   |  hash |     |                            |          |             |
   |  algo |     |                            |          |             |
   | rithm |     |                            |          |             |
   +-------+-----+----------------------------+----------+-------------+


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.

   +---------+-------+---------------------------+---------------------+
   | Algorit | JWE   | XML ENC                   | JCA                 |
   | hm      |       |                           |                     |
   +---------+-------+---------------------------+---------------------+
   | RSA     | RSA1_ | http://www.w3.org/2001/04 | RSA/ECB/PKCS1Paddin |
   | using   | 5     | /xmlenc#rsa-1_5           | g                   |
   | RSA-PKC |       |                           |                     |
   | S1-1.5  |       |                           |                     |
   |  paddin |       |                           |                     |
   | g       |       |                           |                     |







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   | RSA     | RSA-O | http://www.w3.org/2001/04 | RSA/ECB/OAEPWithSHA |
   | using   | AEP   | /xmlenc#rsa-oaep-mgf1p    | -1AndMGF1Padding    |
   | Optimal |       |                           |                     |
   | Asymmet |       |                           |                     |
   | ric     |       |                           |                     |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Paddi |       |                           |                     |
   | ng(OAEP |       |                           |                     |
   | )       |       |                           |                     |
   | Ellipti | ECDH- | http://www.w3.org/2009/xm | TBD                 |
   | cCurve  | ES    | lenc11#ECDH-ES            |                     |
   |  Diffie |       |                           |                     |
   | -Hellma |       |                           |                     |
   | n Ephem |       |                           |                     |
   | eral    |       |                           |                     |
   |    Stat |       |                           |                     |
   | ic      |       |                           |                     |
   | Advance | A128K | http://www.w3.org/2001/04 | TBD                 |
   | d       | W     | /xmlenc#kw-aes128         |                     |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  Key  |       |                           |                     |
   |    Wrap |       |                           |                     |
   |    Algo |       |                           |                     |
   | rithm R |       |                           |                     |
   | FC  339 |       |                           |                     |
   | 4   [RF |       |                           |                     |
   | C3394]  |       |                           |                     |
   | using12 |       |                           |                     |
   | 8 bitke |       |                           |                     |
   | ys      |       |                           |                     |

















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   | Advance | A256K | http://www.w3.org/2001/04 | TBD                 |
   | d       | W     | /xmlenc#kw-aes256         |                     |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  Key  |       |                           |                     |
   |    Wrap |       |                           |                     |
   |    Algo |       |                           |                     |
   | rithm R |       |                           |                     |
   | FC  339 |       |                           |                     |
   | 4   [RF |       |                           |                     |
   | C3394]  |       |                           |                     |
   | using25 |       |                           |                     |
   | 6 bitke |       |                           |                     |
   | ys      |       |                           |                     |
   | Advance | A128C | http://www.w3.org/2001/04 | AES/CBC/PKCS5Paddin |
   | d       | BC    | /xmlenc#aes128-cbc        | g                   |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  usin |       |                           |                     |
   | g  128  |       |                           |                     |
   | bitkeys |       |                           |                     |
   |  inCiph |       |                           |                     |
   | er Bloc |       |                           |                     |
   | k  Chai |       |                           |                     |
   | ning(CB |       |                           |                     |
   | C)  mod |       |                           |                     |
   | e   usi |       |                           |                     |
   | ng  PKC |       |                           |                     |
   | S #5pad |       |                           |                     |
   | ding    |       |                           |                     |

















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   | Advance | A256C | http://www.w3.org/2001/04 | AES/CBC/PKCS5Paddin |
   | d       | BC    | /xmlenc#aes256-cbc        | g                   |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  usin |       |                           |                     |
   | g  256  |       |                           |                     |
   | bitkeys |       |                           |                     |
   |  inCiph |       |                           |                     |
   | er Bloc |       |                           |                     |
   | k  Chai |       |                           |                     |
   | ning(CB |       |                           |                     |
   | C)  mod |       |                           |                     |
   | e   usi |       |                           |                     |
   | ng  PKC |       |                           |                     |
   | S #5pad |       |                           |                     |
   | ding    |       |                           |                     |
   | Advance | A128G | http://www.w3.org/2009/xm | AES/GCM/NoPadding   |
   | d       | CM    | lenc11#aes128-gcm         |                     |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  usin |       |                           |                     |
   | g  128  |       |                           |                     |
   | bitkeys |       |                           |                     |
   |  inGalo |       |                           |                     |
   | is/Coun |       |                           |                     |
   | ter Mod |       |                           |                     |
   | e   (GC |       |                           |                     |
   | M)      |       |                           |                     |
   | Advance | A256G | http://www.w3.org/2009/xm | AES/GCM/NoPadding   |
   | d       | CM    | lenc11#aes256-gcm         |                     |
   |  Encryp |       |                           |                     |
   | tion    |       |                           |                     |
   |   Stand |       |                           |                     |
   | ard(AES |       |                           |                     |
   | )  usin |       |                           |                     |
   | g  256  |       |                           |                     |
   | bitkeys |       |                           |                     |
   |  inGalo |       |                           |                     |
   | is/Coun |       |                           |                     |
   | ter Mod |       |                           |                     |
   | e   (GC |       |                           |                     |
   | M)      |       |                           |                     |
   +---------+-------+---------------------------+---------------------+




Jones                   Expires November 13, 2012              [Page 24]


Internet-Draft          JSON Web Algorithms (JWA)               May 2012


Appendix C.  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.  Dirk Balfanz, John Bradley, Yaron Y.
   Goland, John Panzer, Nat Sakimura, and Paul Tarjan all made
   significant contributions to the design of this specification and its
   related specifications.


Appendix D.  Document History

   -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
      Integrity Value.

   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.

   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.





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Internet-Draft          JSON Web Algorithms (JWA)               May 2012


   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.

   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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