JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track December 27, 2012
Expires: June 30, 2013
JSON Web Key (JWK)
draft-ietf-jose-json-web-key-08
Abstract
A JSON Web Key (JWK) is a JavaScript Object Notation (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
for use with this specification are described in the separate JSON
Web Algorithms (JWA) specification.
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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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 June 30, 2013.
Copyright Notice
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document authors. All rights reserved.
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Example JSON Web Key Set . . . . . . . . . . . . . . . . . . . 4
4. JSON Web Key (JWK) Format . . . . . . . . . . . . . . . . . . 4
4.1. "kty" (Key Type) Parameter . . . . . . . . . . . . . . . . 5
4.2. "use" (Key Use) Parameter . . . . . . . . . . . . . . . . 5
4.3. "alg" (Algorithm) Parameter . . . . . . . . . . . . . . . 5
4.4. "kid" (Key ID) Parameter . . . . . . . . . . . . . . . . . 6
5. JSON Web Key Set (JWK Set) Format . . . . . . . . . . . . . . 6
5.1. "keys" (JSON Web Key Set) Parameter . . . . . . . . . . . 6
6. String Comparison Rules . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
7.1. JSON Web Key Parameters Registry . . . . . . . . . . . . . 7
7.1.1. Registration Template . . . . . . . . . . . . . . . . 8
7.1.2. Initial Registry Contents . . . . . . . . . . . . . . 8
7.2. JSON Web Key Set Parameters Registry . . . . . . . . . . . 8
7.2.1. Registration Template . . . . . . . . . . . . . . . . 9
7.2.2. Initial Registry Contents . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 11
Appendix B. Open Issues . . . . . . . . . . . . . . . . . . . . . 11
Appendix C. Document History . . . . . . . . . . . . . . . . . . 11
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
A JSON Web Key (JWK) is a JavaScript Object Notation (JSON) [RFC4627]
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
for use with this specification are described in the separate JSON
Web Algorithms (JWA) [JWA] specification.
Goals for this specification do not include representing private
keys, representing symmetric keys, representing certificate chains,
representing certified keys, and replacing X.509 certificates.
However the JSON Private and Symmetric Key [JPSK] specification does
extend this specification to define JSON representations of private
keys and symmetric keys.
JWKs and JWK Sets are used in the JSON Web Signature (JWS) [JWS] and
JSON Web Encryption (JWE) [JWE] specifications.
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
JSON Web Key (JWK) A JSON object that represents a public key.
JSON Web Key Set (JWK Set) A JSON object that contains an array of
JWKs as the value of its "keys" member.
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.)
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
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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.
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. The second specifies that the key is to be used with the
"RS256" algorithm. 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.)
{"keys":
[
{"kty":"EC",
"crv":"P-256",
"x":"MKBCTNIcKUSDii11ySs3526iDZ8AiTo7Tu6KPAqv7D4",
"y":"4Etl6SRW2YiLUrN5vfvVHuhp7x8PxltmWWlbbM4IFyM",
"use":"enc",
"kid":"1"},
{"kty":"RSA",
"n": "0vx7agoebGcQSuuPiLJXZptN9nndrQmbXEps2aiAFbWhM78LhWx
4cbbfAAtVT86zwu1RK7aPFFxuhDR1L6tSoc_BJECPebWKRXjBZCiFV4n3oknjhMs
tn64tZ_2W-5JsGY4Hc5n9yBXArwl93lqt7_RN5w6Cf0h4QyQ5v-65YGjQR0_FDW2
QvzqY368QQMicAtaSqzs8KJZgnYb9c7d0zgdAZHzu6qMQvRL5hajrn1n91CbOpbI
SD08qNLyrdkt-bFTWhAI4vMQFh6WeZu0fM4lFd2NcRwr3XPksINHaQ-G_xBniIqb
w0Ls1jF44-csFCur-kEgU8awapJzKnqDKgw",
"e":"AQAB",
"alg":"RS256",
"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.
In addition to the common parameters, each JWK will have members that
are specific to the key being represented. These members represent
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the parameters of the key. Section 5 of the JSON Web Algorithms
(JWA) [JWA] specification defines multiple kinds of public keys and
their associated members.
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. Member names used for
representing key parameters for different kinds of keys need not be
distinct. Any new member name SHOULD either be registered in the
IANA JSON Web Key Parameters registry Section 7.1 or be a value that
contains a Collision Resistant Namespace.
4.1. "kty" (Key Type) Parameter
The "kty" (key type) member identifies the cryptographic algorithm
family used with the key. "kty" values SHOULD either be registered in
the IANA JSON Web Key Types registry [JWA] or be a value that
contains a Collision Resistant Namespace. The "kty" value is a case
sensitive string. Use of this member is REQUIRED.
A list of defined "kty" values can be found in the IANA JSON Web Key
Types registry [JWA]; the initial contents of this registry are the
values defined in Section 5.1 of the JSON Web Algorithms (JWA) [JWA]
specification.
Additional members used with these "kty" values can be found in the
IANA JSON Web Key Parameters registry Section 7.1; the initial
contents of this registry are the values defined in Sections 5.2 and
5.3 of the JSON Web Algorithms (JWA) [JWA] specification.
4.2. "use" (Key Use) Parameter
The "use" (key use) member identifies the intended use of the key.
Values defined by this specification are:
o "sig" (signature)
o "enc" (encryption)
Other values MAY be used. The "use" value is a case sensitive
string. Use of this member is OPTIONAL.
4.3. "alg" (Algorithm) Parameter
The "alg" (algorithm) member identifies the algorithm intended for
use with the key. The values used in this field are the same as
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those used in the JWS [JWS] and JWE [JWE] "alg" and "enc" header
parameters; these values can be found in the JSON Web Signature and
Encryption Algorithms registry [JWA]. Use of this member is
OPTIONAL.
4.4. "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 a JWK
Set during key rollover. The interpretation of the "kid" value is
unspecified. Key ID values within a JWK Set need not be unique. The
"kid" value is a case sensitive string. Use of this member is
OPTIONAL.
When used with JWS or JWE, the "kid" value MAY be used to match a JWS
or JWE "kid" header parameter value.
In some contexts, different keys using the same Key ID value might be
present, with the keys being disambiguated using other information,
such as the "kty" or "use" values. For example, imagine "kid" values
like "Current", "Upcoming", and "Deprecated", used for key rollover
guidance. One could apply a label to all keys where the
classification fits. If there are multiple "Current" keys, then in
this example, they might be differentiated either by having different
"kty" or "use" values, or some combination of both. As one example,
there might only be one current RSA signing key and one current
Elliptic Curve signing key, but both would be "Current".
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
registered in the IANA JSON Web Key Set Parameters registry
Section 7.2 or be a value 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. Use of this member is REQUIRED.
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6. String Comparison Rules
Processing a JWK inevitably requires comparing known strings to
values in JSON objects. For example, in checking what the key type
is, the Unicode string encoding "kty" will be checked against the
member names in the JWK to see if there is a matching name.
Comparisons between JSON strings and other Unicode strings MUST be
performed by comparing Unicode code points without normalization as
specified in the String Comparison Rules in Section 5.3 of [JWS].
7. 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.
7.1. JSON Web Key Parameters Registry
This specification establishes the IANA JSON Web Key Parameters
registry for reserved JWK parameter names. The registry records the
reserved parameter name and a reference to the specification that
defines it. This specification registers the parameter names defined
in Section 4. The same JWK parameter name may be registered multiple
times, provided that duplicate parameter registrations are only for
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algorithm-specific JWK parameters; in this case, the meaning of the
duplicate parameter name is disambiguated by the "kty" value of the
JWK containing it.
7.1.1. Registration Template
Parameter 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.
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.
7.1.2. Initial Registry Contents
o Parameter Name: "kty"
o Change Controller: IETF
o Specification Document(s): Section 4.1 of [[ this document ]]
o Parameter Name: "use"
o Change Controller: IETF
o Specification Document(s): Section 4.2 of [[ this document ]]
o Parameter Name: "alg"
o Change Controller: IETF
o Specification Document(s): Section 4.3 of [[ this document ]]
o Parameter Name: "kid"
o Change Controller: IETF
o Specification Document(s): Section 4.4 of [[ this document ]]
7.2. JSON Web Key Set Parameters Registry
This specification establishes the IANA JSON Web Key Set Parameters
registry for reserved JWK Set parameter names. The registry records
the reserved parameter name and a reference to the specification that
defines it. This specification registers the parameter names defined
in Section 5.
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7.2.1. Registration Template
Parameter 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.
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.
7.2.2. Initial Registry Contents
o Parameter Name: "keys"
o Change Controller: IETF
o Specification Document(s): Section 5.1 of [[ this document ]]
8. 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.
A key is no more trustworthy than the method by which it was
received.
Per Section 4.4, applications should not assume that "kid" values are
unique within a JWK Set.
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.
9. References
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9.1. Normative References
[JWA] Jones, M., "JSON Web Algorithms (JWA)",
draft-ietf-jose-json-web-algorithms (work in progress),
December 2012.
[JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
Encryption (JWE)", draft-ietf-jose-json-web-encryption
(work in progress), December 2012.
[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", draft-ietf-jose-json-web-signature (work
in progress), December 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.
[W3C.CR-xmldsig-core2-20120124]
Yiu, K., Solo, D., Eastlake, D., Datta, P., Hirsch, F.,
Reagle, J., 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>.
9.2. Informative References
[JPSK] Jones, M., "JSON Private and Symmetric Key",
draft-ietf-jose-json-private-and-symmetric-key (work in
progress), December 2012.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", January 2011.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
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Appendix A. Acknowledgements
A JSON representation for RSA public keys was previously introduced
by John Panzer, Ben Laurie, and Dirk Balfanz in Magic Signatures
[MagicSignatures].
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, Joe Hildebrand, Edmund Jay, Ben Laurie, James Manger, Tony
Nadalin, Axel Nennker, John Panzer, Eric Rescorla, Nat Sakimura, Jim
Schaad, Paul Tarjan, 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 B. Open Issues
[[ to be removed by the RFC editor before publication as an RFC ]]
The following items remain to be considered or done in this draft:
o No known open issues.
Appendix C. Document History
[[ to be removed by the RFC editor before publication as an RFC ]]
-08
o Changed the name of the JWK key type parameter from "alg" to "kty"
to enable use of "alg" to indicate the particular algorithm that
the key is intended to be used with.
o Clarified statements of the form "This member is OPTIONAL" to "Use
of this member is OPTIONAL".
o Referenced String Comparison Rules in JWS.
o Added seriesInfo information to Internet Draft references.
-07
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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.
-06
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
specification.)
o Clarify that the "alg" (algorithm family) member is REQUIRED.
o Correct an instance of "JWK" that should have been "JWK Set".
o Applied changes made by the RFC Editor to RFC 6749's registry
language to this specification.
-05
o Indented artwork elements to better distinguish them from the body
text.
-04
o Refer to the registries as the primary sources of defined values
and then secondarily reference the sections defining the initial
contents of the registries.
o Normatively reference XML DSIG 2.0 [W3C.CR-xmldsig-core2-20120124]
for its security considerations.
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 Clarified that "kid" values need not be unique within a JWK Set.
o Moved JSON Web Key Parameters registry to the JWK specification.
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o Added "Collision Resistant Namespace" to the terminology section.
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 Numerous editorial improvements.
-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.
-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.
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Author's Address
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
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