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JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track January 16, 2012
Expires: July 19, 2012
JSON Web Key (JWK)
draft-ietf-jose-json-web-key-00
Abstract
A JSON Web Key (JWK) is a JSON data structure that represents a set
of public keys.
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 July 19, 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
to this document. Code Components extracted from this document must
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. JSON Web Key (JWK) Overview . . . . . . . . . . . . . . . . . . 3
3.1. Example JWK . . . . . . . . . . . . . . . . . . . . . . . . 3
4. JWK Format . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. JWK Container Object Format . . . . . . . . . . . . . . . . 4
4.2. JWK Key Object Format . . . . . . . . . . . . . . . . . . . 5
4.2.1. JWK Key Object Members for Elliptic Curve Keys . . . . 5
4.2.2. JWK Key Object Members for RSA Keys . . . . . . . . . . 6
5. Base64url encoding as used by JWKs . . . . . . . . . . . . . . 7
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
8. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 8
Appendix B. Document History . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
A JSON Web Key (JWK) is a JSON data structure that represents a set
of public keys as a JSON object [RFC4627]. The JWK format is used to
represent bare keys; representing certificate chains is an explicit
non-goal of this specification. JSON Web Keys are referenced in JSON
Web Signature (JWS) [JWS] using the "jku" (JSON Key URL) header
parameter and in JSON Web Encryption (JWE) [JWE] using the "jku"
(JSON Key URL) and "epk" (Ephemeral Public Key) header parameters.
2. Terminology
JSON Web Key (JWK) A JSON data structure that represents a set of
public keys. A JWK consists of a single JWK Container Object that
contains an array of JWK Key Objects.
JWK Container Object A JSON object that contains an array of JWK Key
Objects as a member.
JWK Key Object A JSON object that represents a single public key.
Base64url Encoding For the purposes of this specification, this term
always refers to 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 B of [JWS] for notes on implementing base64url
encoding without padding.)
3. JSON Web Key (JWK) Overview
It is sometimes useful to be able to reference public key
representations, for instance, in order to verify the digital
signature on content signed with the corresponding private key. The
JSON Web Key (JWK) data structure provides a convenient JSON
representation for sets of public keys utilizing either the Elliptic
Curve or RSA families of algorithms.
3.1. Example JWK
The following example JWK contains two public keys: one using an
Elliptic Curve algorithm and a second one using an RSA algorithm.
The first specifies that the key is to be used for encryption. Both
provide a Key ID for matching purposes. In both cases, integers are
represented using the base64url encoding of their big endian
representations. (Long lines are broken are for display purposes
only.)
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{"jwk":
[
{"alg":"EC",
"crv":"P-256",
"x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4",
"y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM",
"use":"enc",
"kid":"1"},
{"alg":"RSA",
"mod": "0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx
4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMs
tn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2
QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbI
SD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqb
w0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw",
"exp":"AQAB",
"kid":"2011-04-29"}
]
}
4. JWK Format
A JWK consists of a JWK Container Object, which is a JSON object that
contains an array of JWK Key Objects as a member. This section
specifies the format of these objects.
4.1. JWK Container Object Format
A JWK Container Object is a JSON object containing a specific member.
This member is:
+--------+----------+-----------------------------------------------+
| Member | JSON | Container Object Member Semantics |
| Name | Value | |
| | Type | |
+--------+----------+-----------------------------------------------+
| jwk | array | The "jwk" member value contains an array of |
| | | JWK Key Objects. This member is REQUIRED. |
+--------+----------+-----------------------------------------------+
JWK Container Object Member
Additional members MAY be present in the JWK Container Object. If
present, they MUST be understood by implementations using that JWK.
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4.2. JWK Key Object Format
A JWK Key Object is a JSON object containing specific members. Those
members that are common to all key types are as follows:
+--------+--------+-------------------------------------------------+
| Member | JSON | Key Object Member Semantics |
| Name | Value | |
| | Type | |
+--------+--------+-------------------------------------------------+
| alg | string | The "alg" member identifies the cryptographic |
| | | algorithm family used with the key. Values |
| | | defined by this specification are "EC" and |
| | | "RSA". Specific additional members are |
| | | required to represent the key, depending upon |
| | | the "alg" value. The "alg" value is case |
| | | sensitive. This member is REQUIRED. |
| use | string | The "use" member identifies the intended use of |
| | | the key. Values defined by this specification |
| | | are "sig" (signature) and "enc" (encryption). |
| | | Other values MAY be used. The "use" value is |
| | | case sensitive. This member is OPTIONAL. |
| kid | string | The "kid" (Key ID) member can be used to match |
| | | a specific key. This can be used, for |
| | | instance, to choose among a set of keys within |
| | | the JWK during key rollover. The "kid" value |
| | | MAY correspond to a JWS "kid" value. The |
| | | interpretation of the "kid" value is |
| | | unspecified. This member is OPTIONAL. |
+--------+--------+-------------------------------------------------+
JWK Key Object Members
Additional members MAY be present in the JWK Key Object. If present,
they MUST be understood by implementations using that key.
4.2.1. JWK Key Object Members 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:
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+--------+--------+-------------------------------------------------+
| Member | JSON | Key Object Member Semantics |
| Name | Value | |
| | Type | |
+--------+--------+-------------------------------------------------+
| crv | string | The "crv" 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. |
| x | string | The "x" member contains the x coordinate for |
| | | the elliptic curve point. It is represented as |
| | | the base64url encoding of the coordinate's big |
| | | endian representation. |
| y | string | The "y" member contains the y coordinate for |
| | | the elliptic curve point. It is represented as |
| | | the base64url encoding of the coordinate's big |
| | | endian representation. |
+--------+--------+-------------------------------------------------+
Members for Elliptic Curve Keys
4.2.2. JWK Key Object Members 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:
+--------+--------+-------------------------------------------------+
| Member | JSON | Key Object Member Semantics |
| Name | Value | |
| | Type | |
+--------+--------+-------------------------------------------------+
| mod | string | The "mod" member contains the modulus value for |
| | | the RSA public key. It is represented as the |
| | | base64url encoding of the value's big endian |
| | | representation. |
| exp | string | The "exp" member contains the exponent value |
| | | for the RSA public key. It is represented as |
| | | the base64url encoding of the value's big |
| | | endian representation. |
+--------+--------+-------------------------------------------------+
Members for RSA Keys
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5. Base64url encoding as used by JWKs
JWKs make use of the base64url encoding as defined in RFC 4648
[RFC4648]. As allowed by Section 3.2 of the RFC, this specification
mandates that base64url encoding when used with JWKs MUST NOT use
padding. Notes on implementing base64url encoding can be found in
the JWS [JWS] specification.
6. IANA Considerations
No IANA actions are required by this specification.
7. Security Considerations
TBD
8. Open Issues and Things To Be Done (TBD)
The following items remain to be done in this draft:
o Write the Security Considerations section.
9. References
9.1. Normative References
[FIPS.186-3]
National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", FIPS PUB 186-3, June 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[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.
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9.2. Informative References
[JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
Encryption (JWE)", January 2012.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", January 2012.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", August 2010.
Appendix A. Acknowledgements
A JSON representation for RSA public keys was previously introduced
in Magic Signatures [MagicSignatures].
Appendix B. Document History
-00
o Created the initial IETF draft based upon
draft-jones-json-web-key-03 with no normative changes.
Author's Address
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
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