JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track May 12, 2012
Expires: November 13, 2012
JSON Web Key (JWK)
draft-ietf-jose-json-web-key-02
Abstract
A JSON Web Key (JWK) is a JSON data structure that represents a
public key. This specification also defines a JSON Web Key Set (JWK
Set) JSON data structure for representing a set of JWKs.
Cryptographic algorithms and identifiers used with this specification
are enumerated in the separate JSON Web Algorithms (JWA)
specification.
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
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provisions of BCP 78 and BCP 79.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Example JSON Web Key Set . . . . . . . . . . . . . . . . . . . 3
4. JSON Web Key (JWK) Format . . . . . . . . . . . . . . . . . . . 4
4.1. "alg" (Algorithm Family) Parameter . . . . . . . . . . . . 4
4.2. "use" (Key Use) Parameter . . . . . . . . . . . . . . . . . 5
4.3. "kid" (Key ID) Parameter . . . . . . . . . . . . . . . . . 5
5. JSON Web Key Set (JWK Set) Format . . . . . . . . . . . . . . . 5
5.1. "keys" (JSON Web Key Set) Parameter . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6.1. JSON Web Key Set Parameters Registry . . . . . . . . . . . 6
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
8. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . . 6
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
9.1. Normative References . . . . . . . . . . . . . . . . . . . 6
9.2. Informative References . . . . . . . . . . . . . . . . . . 7
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 7
Appendix B. Document History . . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
A JSON Web Key (JWK) is a JSON data structure that represents a
public key as a JSON object [RFC4627]. This specification also
defines a JSON Web Key Set (JWK Set) JSON data structure for
representing a set of JWKs. Cryptographic algorithms and identifiers
used with this specification are enumerated in the separate JSON Web
Algorithms (JWA) [JWA] specification.
Non-goals for this specification include representing private keys,
representing symmetric keys, representing certificate chains,
representing certified keys, and replacing X.509 certificates.
JWKs are used in the JSON Web Signature (JWS) [JWS] "jwk" (JSON Web
Key) header parameter and the JSON Web Encryption (JWE) [JWE] "jwk"
(JSON Web Key) and "epk" (Ephemeral Public Key) header parameters.
The resources referenced by the JWS "jku" (JWK Set URL) and JWE "jku"
(JWK Set URL) header parameters contain JWK Sets.
2. Terminology
JSON Web Key (JWK) A JSON data structure that represents a public
key.
JSON Web Key Set (JWK Set) A JSON object that contains an array of
JWKs as a member.
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. Example JSON Web Key Set
The following example JWK Set contains two public keys represented as
JWKs: 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 key 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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{"keys":
[
{"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. JSON Web Key (JWK) Format
A JSON Web Key (JWK) is a JSON object containing specific members, as
specified below. Those members that are common to all key types are
defined below.
JWKs also require members that are specific to the particular key
algorithm family to represent the key parameters. These algorithm
specific members are defined in Section 5 of the JSON Web Algorithms
(JWA) [JWA] specification.
The member names within a JWK MUST be unique; objects with duplicate
member names MUST be rejected.
Additional members MAY be present in the JWK. If present, they MUST
be understood by implementations using them. Parameters for
representing keys for additional algorithm families or additional key
properties SHOULD either be defined in the IANA JSON Web Key
Parameters registry [JWA] or be a URI that contains a collision
resistant namespace.
4.1. "alg" (Algorithm Family) Parameter
The "alg" (algorithm family) member identifies the cryptographic
algorithm family used with the key. A list of defined "alg" values
is presented in Section 5.1 of the JSON Web Algorithms (JWA) [JWA]
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specification. Specific additional members are required to represent
the key, depending upon the algorithm family. These members are
specified in Section 5 of the JSON Web Algorithms (JWA) [JWA]
specification. The "alg" value is case sensitive. Its value MUST be
a string.
"alg" values SHOULD either be defined in the IANA JSON Web Key
Algorithm Families registry [JWA] or be a URI that contains a
collision resistant namespace.
4.2. "use" (Key Use) Parameter
The "use" (key 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. Its value MUST be a string. This member is OPTIONAL.
4.3. "kid" (Key ID) Parameter
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. When used with JWS or JWE, the "kid" value
MAY be used to match a JWS or JWE "kid" header parameter value. The
interpretation of the "kid" value is unspecified. Its value MUST be
a string. This member is OPTIONAL.
5. JSON Web Key Set (JWK Set) Format
A JSON Web Key Set (JWK Set) is a JSON object that contains an array
of JSON Web Key values as the value of its "keys" member.
The member names within a JWK Set MUST be unique; objects with
duplicate member names MUST be rejected.
Additional members MAY be present in the JWK Set. If present, they
MUST be understood by implementations using them. Parameters for
representing additional properties of JWK Sets SHOULD either be
defined in the IANA JSON Web Key Set Parameters registry Section 6.1
or be a URI that contains a collision resistant namespace.
5.1. "keys" (JSON Web Key Set) Parameter
The value of the "keys" (JSON Web Key Set) member is an array of JSON
Web Key (JWK) values. This member is REQUIRED.
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6. IANA Considerations
6.1. JSON Web Key Set Parameters Registry
This specification establishes the IANA JSON Web Key Set Parameters
registry for reserved JWK Set 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 Section 5.
7. Security Considerations
A key is no more trustworthy than the method by which it was
received.
The security considerations in XML DSIG 2.0
[W3C.CR-xmldsig-core2-20120124], about public key representations
also apply to this specification, other than those that are XML
specific.
8. Open Issues and Things To Be Done (TBD)
The following items remain to be done in this draft:
o (None at present)
9. References
9.1. Normative References
[JWA] Jones, M., "JSON Web Algorithms (JWA)", May 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
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9.2. Informative References
[JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
Encryption (JWE)", May 2012.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", May 2012.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", January 2011.
[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>.
Appendix A. Acknowledgements
A JSON representation for RSA public keys was previously introduced
in Magic Signatures [MagicSignatures].
Appendix B. Document History
-02
o Simplified JWK terminology to get replace the "JWK Key Object" and
"JWK Container Object" terms with simply "JSON Web Key (JWK)" and
"JSON Web Key Set (JWK Set)" and to eliminate potential confusion
between single keys and sets of keys. As part of this change, the
top-level member name for a set of keys was changed from "jwk" to
"keys".
o Clarified that values with duplicate member names MUST be
rejected.
o Established JSON Web Key Set Parameters registry.
o Explicitly listed non-goals in the introduction.
o Moved algorithm-specific definitions from JWK to JWA.
o Reformatted to give each member definition its own section
heading.
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-01
o Corrected the Magic Signatures reference.
-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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