| Rfc | 7800 |
|---|
| Title | Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs) |
|---|
| Author | M.
Jones, J. Bradley, H. Tschofenig |
|---|
| Date | April 2016 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | PROPOSED STANDARD |
|---|
|
Internet Engineering Task Force (IETF) M. Jones
Request for Comments: 7800 Microsoft
Category: Standards Track J. Bradley
ISSN: 2070-1721 Ping Identity
H. Tschofenig
ARM Limited
April 2016
Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)
Abstract
This specification describes how to declare in a JSON Web Token (JWT)
that the presenter of the JWT possesses a particular proof-of-
possession key and how the recipient can cryptographically confirm
proof of possession of the key by the presenter. Being able to prove
possession of a key is also sometimes described as the presenter
being a holder-of-key.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7800.
Copyright Notice
Copyright (c) 2016 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
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Representations for Proof-of-Possession Keys . . . . . . . . 5
3.1. Confirmation Claim . . . . . . . . . . . . . . . . . . . 6
3.2. Representation of an Asymmetric Proof-of-Possession Key . 7
3.3. Representation of an Encrypted Symmetric Proof-of-
Possession Key . . . . . . . . . . . . . . . . . . . . . 7
3.4. Representation of a Key ID for a Proof-of-Possession Key 8
3.5. Representation of a URL for a Proof-of-Possession Key . . 9
3.6. Specifics Intentionally Not Specified . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6.1. JSON Web Token Claims Registration . . . . . . . . . . . 12
6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 12
6.2. JWT Confirmation Methods Registry . . . . . . . . . . . . 12
6.2.1. Registration Template . . . . . . . . . . . . . . . . 12
6.2.2. Initial Registry Contents . . . . . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . 14
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction
This specification describes how a JSON Web Token [JWT] can declare
that the presenter of the JWT possesses a particular proof-of-
possession (PoP) key and how the recipient can cryptographically
confirm proof of possession of the key by the presenter. Proof of
possession of a key is also sometimes described as the presenter
being a holder-of-key. The [OAUTH-POP-ARCH] specification describes
key confirmation, among other confirmation mechanisms. This
specification defines how to communicate confirmation key information
in JWTs.
Envision the following two use cases. The first use case employs a
symmetric proof-of-possession key and the second use case employs an
asymmetric proof-of-possession key.
+--------------+
| | +--------------+
| |--(3) Presentation of -->| |
| | JWT w/ Encrypted | |
| Presenter | PoP Key | |
| | | |
| |<-(4) Communication ---->| |
| | Authenticated by | |
+--------------+ PoP Key | |
^ ^ | |
| | | |
(1) Sym. (2) JWT w/ | Recipient |
| PoP | Encrypted | |
| Key | PoP Key | |
v | | |
+--------------+ | |
| | | |
| | | |
| |<-(0) Key Exchange for ->| |
| Issuer | Key Encryption Key | |
| | | |
| | | |
| | +--------------+
+--------------+
Figure 1: Proof of Possession with a Symmetric Key
In the case illustrated in Figure 1, (1) either the presenter
generates a symmetric key and privately sends it to the issuer or the
issuer generates a symmetric key and privately sends it to the
presenter. The issuer generates a JWT with an encrypted copy of this
symmetric key in the confirmation claim. This symmetric key is
encrypted with a key known only to the issuer and the recipient,
which was previously established in step (0). The entire JWT is
integrity protected by the issuer. The JWT is then (2) sent to the
presenter. Now, the presenter is in possession of the symmetric key
as well as the JWT (which includes the confirmation claim). When the
presenter (3) presents the JWT to the recipient, it also needs to
demonstrate possession of the symmetric key; the presenter, for
example, (4) uses the symmetric key in a challenge/response protocol
with the recipient. The recipient is then able to verify that it is
interacting with the genuine presenter by decrypting the key in the
confirmation claim of the JWT. By doing this, the recipient obtains
the symmetric key, which it then uses to verify cryptographically
protected messages exchanged with the presenter (4). This symmetric
key mechanism described above is conceptually similar to the use of
Kerberos tickets.
Note that for simplicity, the diagram above and associated text
describe the direct use of symmetric keys without the use of derived
keys. A more secure practice is to derive the symmetric keys
actually used from secrets exchanged, such as the key exchanged in
step (0), using a Key Derivation Function (KDF) and use the derived
keys, rather than directly using the secrets exchanged.
+--------------+
| | +--------------+
| |--(3) Presentation of -->| |
| | JWT w/ Public | |
| Presenter | PoP Key | |
| | | |
| |<-(4) Communication ---->| |
| | Authenticated by | |
+--------------+ PoP Key | |
| ^ | |
| | | |
(1) Public (2) JWT w/ | Recipient |
| PoP | Public | |
| Key | PoP Key | |
v | | |
+--------------+ | |
| | | |
| | | |
| | | |
| Issuer | | |
| | | |
| | | |
| | +--------------+
+--------------+
Figure 2: Proof of Possession with an Asymmetric Key
In the case illustrated in Figure 2, the presenter generates a
public/private key pair and (1) sends the public key to the issuer,
which creates a JWT that contains the public key (or an identifier
for it) in the confirmation claim. The entire JWT is integrity
protected using a digital signature to protect it against
modifications. The JWT is then (2) sent to the presenter. When the
presenter (3) presents the JWT to the recipient, it also needs to
demonstrate possession of the private key. The presenter, for
example, (4) uses the private key in a Transport Layer Security (TLS)
exchange with the recipient or (4) signs a nonce with the private
key. The recipient is able to verify that it is interacting with the
genuine presenter by extracting the public key from the confirmation
claim of the JWT (after verifying the digital signature of the JWT)
and utilizing it with the private key in the TLS exchange or by
checking the nonce signature.
In both cases, the JWT may contain other claims that are needed by
the application.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in RFC
2119 [RFC2119].
Unless otherwise noted, all the protocol parameter names and values
are case sensitive.
2. Terminology
This specification uses terms defined in the JSON Web Token [JWT],
JSON Web Key [JWK], and JSON Web Encryption [JWE] specifications.
These terms are defined by this specification:
Issuer
Party that creates the JWT and binds the proof-of-possession key
to it.
Presenter
Party that proves possession of a private key (for asymmetric key
cryptography) or secret key (for symmetric key cryptography) to a
recipient.
Recipient
Party that receives the JWT containing the proof-of-possession key
information from the presenter.
3. Representations for Proof-of-Possession Keys
By including a "cnf" (confirmation) claim in a JWT, the issuer of the
JWT declares that the presenter possesses a particular key and that
the recipient can cryptographically confirm that the presenter has
possession of that key. The value of the "cnf" claim is a JSON
object and the members of that object identify the proof-of-
possession key.
The presenter can be identified in one of several ways by the JWT
depending upon the application requirements. If the JWT contains a
"sub" (subject) claim [JWT], the presenter is normally the subject
identified by the JWT. (In some applications, the subject identifier
will be relative to the issuer identified by the "iss" (issuer) claim
[JWT].) If the JWT contains no "sub" claim, the presenter is
normally the issuer identified by the JWT using the "iss" claim. The
case in which the presenter is the subject of the JWT is analogous to
Security Assertion Markup Language (SAML) 2.0
[OASIS.saml-core-2.0-os] SubjectConfirmation usage. At least one of
the "sub" and "iss" claims MUST be present in the JWT. Some use
cases may require that both be present.
Another means used by some applications to identify the presenter is
an explicit claim, such as the "azp" (authorized party) claim defined
by OpenID Connect [OpenID.Core]. Ultimately, the means of
identifying the presenter is application specific, as is the means of
confirming possession of the key that is communicated.
3.1. Confirmation Claim
The "cnf" claim is used in the JWT to contain members used to
identify the proof-of-possession key. Other members of the "cnf"
object may be defined because a proof-of-possession key may not be
the only means of confirming the authenticity of the token. This is
analogous to the SAML 2.0 [OASIS.saml-core-2.0-os]
SubjectConfirmation element in which a number of different subject
confirmation methods can be included (including proof-of-possession
key information).
The set of confirmation members that a JWT must contain to be
considered valid is context dependent and is outside the scope of
this specification. Specific applications of JWTs will require
implementations to understand and process some confirmation members
in particular ways. However, in the absence of such requirements,
all confirmation members that are not understood by implementations
MUST be ignored.
This specification establishes the IANA "JWT Confirmation Methods"
registry for these members in Section 6.2 and registers the members
defined by this specification. Other specifications can register
other members used for confirmation, including other members for
conveying proof-of-possession keys using different key
representations.
The "cnf" claim value MUST represent only a single proof-of-
possession key; thus, at most one of the "jwk", "jwe", and "jku" (JWK
Set URL) confirmation values defined below may be present. Note that
if an application needs to represent multiple proof-of-possession
keys in the same JWT, one way for it to achieve this is to use other
claim names, in addition to "cnf", to hold the additional proof-of-
possession key information. These claims could use the same syntax
and semantics as the "cnf" claim. Those claims would be defined by
applications or other specifications and could be registered in the
IANA "JSON Web Token Claims" registry [IANA.JWT.Claims].
3.2. Representation of an Asymmetric Proof-of-Possession Key
When the key held by the presenter is an asymmetric private key, the
"jwk" member is a JSON Web Key [JWK] representing the corresponding
asymmetric public key. The following example demonstrates such a
declaration in the JWT Claims Set of a JWT:
{
"iss": "https://server.example.com",
"aud": "https://client.example.org",
"exp": 1361398824,
"cnf":{
"jwk":{
"kty": "EC",
"use": "sig",
"crv": "P-256",
"x": "18wHLeIgW9wVN6VD1Txgpqy2LszYkMf6J8njVAibvhM",
"y": "-V4dS4UaLMgP_4fY4j8ir7cl1TXlFdAgcx55o7TkcSA"
}
}
}
The JWK MUST contain the required key members for a JWK of that key
type and MAY contain other JWK members, including the "kid" (Key ID)
member.
The "jwk" member MAY also be used for a JWK representing a symmetric
key, provided that the JWT is encrypted so that the key is not
revealed to unintended parties. The means of encrypting a JWT is
explained in [JWT]. If the JWT is not encrypted, the symmetric key
MUST be encrypted as described below.
3.3. Representation of an Encrypted Symmetric Proof-of-Possession Key
When the key held by the presenter is a symmetric key, the "jwe"
member is an encrypted JSON Web Key [JWK] encrypted to a key known to
the recipient using the JWE Compact Serialization containing the
symmetric key. The rules for encrypting a JWK are found in Section 7
of the JSON Web Key [JWK] specification.
The following example illustrates a symmetric key that could
subsequently be encrypted for use in the "jwe" member:
{
"kty": "oct",
"alg": "HS256",
"k": "ZoRSOrFzN_FzUA5XKMYoVHyzff5oRJxl-IXRtztJ6uE"
}
The UTF-8 [RFC3629] encoding of this JWK is used as the JWE Plaintext
when encrypting the key.
The following example is a JWE Header that could be used when
encrypting this key:
{
"alg": "RSA-OAEP",
"enc": "A128CBC-HS256"
}
The following example JWT Claims Set of a JWT illustrates the use of
an encrypted symmetric key as the "jwe" member value:
{
"iss": "https://server.example.com",
"sub": "24400320",
"aud": "s6BhdRkqt3",
"nonce": "n-0S6_WzA2Mj",
"exp": 1311281970,
"iat": 1311280970,
"cnf":{
"jwe":
"eyJhbGciOiJSU0EtT0FFUCIsImVuYyI6IkExMjhDQkMtSFMyNTYifQ.
(remainder of JWE omitted for brevity)"
}
}
3.4. Representation of a Key ID for a Proof-of-Possession Key
The proof-of-possession key can also be identified by the use of a
Key ID instead of communicating the actual key, provided the
recipient is able to obtain the identified key using the Key ID. In
this case, the issuer of a JWT declares that the presenter possesses
a particular key and that the recipient can cryptographically confirm
proof of possession of the key by the presenter by including a "cnf"
claim in the JWT whose value is a JSON object with the JSON object
containing a "kid" member identifying the key.
The following example demonstrates such a declaration in the JWT
Claims Set of a JWT:
{
"iss": "https://server.example.com",
"aud": "https://client.example.org",
"exp": 1361398824,
"cnf":{
"kid": "dfd1aa97-6d8d-4575-a0fe-34b96de2bfad"
}
}
The content of the "kid" value is application specific. For
instance, some applications may choose to use a JWK Thumbprint
[JWK.Thumbprint] value as the "kid" value.
3.5. Representation of a URL for a Proof-of-Possession Key
The proof-of-possession key can be passed by reference instead of
being passed by value. This is done using the "jku" member. Its
value is a URI [RFC3986] that refers to a resource for a set of JSON-
encoded public keys represented as a JWK Set [JWK], one of which is
the proof-of-possession key. If there are multiple keys in the
referenced JWK Set document, a "kid" member MUST also be included
with the referenced key's JWK also containing the same "kid" value.
The protocol used to acquire the resource MUST provide integrity
protection. An HTTP GET request to retrieve the JWK Set MUST use TLS
[RFC5246] and the identity of the server MUST be validated, as per
Section 6 of RFC 6125 [RFC6125].
The following example demonstrates such a declaration in the JWT
Claims Set of a JWT:
{
"iss": "https://server.example.com",
"sub": "17760704",
"aud": "https://client.example.org",
"exp": 1440804813,
"cnf":{
"jku": "https://keys.example.net/pop-keys.json",
"kid": "2015-08-28"
}
}
3.6. Specifics Intentionally Not Specified
Proof of possession is typically demonstrated by having the presenter
sign a value determined by the recipient using the key possessed by
the presenter. This value is sometimes called a "nonce" or a
"challenge".
The means of communicating the nonce and the nature of its contents
are intentionally not described in this specification, as different
protocols will communicate this information in different ways.
Likewise, the means of communicating the signed nonce is also not
specified, as this is also protocol specific.
Note that another means of proving possession of the key when it is a
symmetric key is to encrypt the key to the recipient. The means of
obtaining a key for the recipient is likewise protocol specific.
For examples using the mechanisms defined in this specification, see
[OAUTH-POP-ARCH].
4. Security Considerations
All of the security considerations that are discussed in [JWT] also
apply here. In addition, proof of possession introduces its own
unique security issues. Possessing a key is only valuable if it is
kept secret. Appropriate means must be used to ensure that
unintended parties do not learn private key or symmetric key values.
Applications utilizing proof of possession should also utilize
audience restriction, as described in Section 4.1.3 of [JWT], as it
provides different protections. Proof of possession can be used by
recipients to reject messages from unauthorized senders. Audience
restriction can be used by recipients to reject messages intended for
different recipients.
A recipient might not understand the "cnf" claim. Applications that
require the proof-of-possession keys communicated with it to be
understood and processed must ensure that the parts of this
specification that they use are implemented.
Proof of possession via encrypted symmetric secrets is subject to
replay attacks. This attack can, for example, be avoided when a
signed nonce or challenge is used since the recipient can use a
distinct nonce or challenge for each interaction. Replay can also be
avoided if a sub-key is derived from a shared secret that is specific
to the instance of the PoP demonstration.
As is the case with other information included in a JWT, it is
necessary to apply data origin authentication and integrity
protection (via a keyed message digest or a digital signature). Data
origin authentication ensures that the recipient of the JWT learns
about the entity that created the JWT since this will be important
for any policy decisions. Integrity protection prevents an adversary
from changing any elements conveyed within the JWT payload. Special
care has to be applied when carrying symmetric keys inside the JWT
since those not only require integrity protection but also
confidentiality protection.
5. Privacy Considerations
A proof-of-possession key can be used as a correlation handle if the
same key is used with multiple parties. Thus, for privacy reasons,
it is recommended that different proof-of-possession keys be used
when interacting with different parties.
6. IANA Considerations
The following registration procedure is used for all the registries
established by this specification.
Values are registered on a Specification Required [RFC5226] basis
after a three-week review period on the jwt-reg-review@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 Experts may approve registration once they are
satisfied that such a specification will be published.
Registration requests sent to the mailing list for review should use
an appropriate subject (e.g., "Request to Register JWT Confirmation
Method: example"). Registration requests that are undetermined for a
period longer than 21 days can be brought to the IESG's attention
(using the iesg@ietf.org mailing list) for resolution.
Criteria that should be applied by the Designated Experts include
determining whether the proposed registration duplicates existing
functionality, determining whether it is likely to be of general
applicability or whether it is useful only for a single application,
and evaluating the security properties of the item being registered
and whether the registration makes sense.
It is suggested that multiple Designated Experts be appointed who are
able to represent the perspectives of different applications using
this specification in order to enable broadly informed review of
registration decisions. In cases where a registration decision could
be perceived as creating a conflict of interest for a particular
Expert, that Expert should defer to the judgment of the other
Experts.
6.1. JSON Web Token Claims Registration
This specification registers the "cnf" claim in the IANA "JSON Web
Token Claims" registry [IANA.JWT.Claims] established by [JWT].
6.1.1. Registry Contents
o Claim Name: "cnf"
o Claim Description: Confirmation
o Change Controller: IESG
o Specification Document(s): Section 3.1 of [RFC7800]
6.2. JWT Confirmation Methods Registry
This specification establishes the IANA "JWT Confirmation Methods"
registry for JWT "cnf" member values. The registry records the
confirmation method member and a reference to the specification that
defines it.
6.2.1. Registration Template
Confirmation Method Value:
The name requested (e.g., "kid"). Because a core goal of this
specification is for the resulting representations to be compact,
it is RECOMMENDED that the name be short -- not to exceed eight
characters without a compelling reason to do so. This name is
case sensitive. Names may not match other registered names in a
case-insensitive manner unless the Designated Experts state that
there is a compelling reason to allow an exception.
Confirmation Method Description:
Brief description of the confirmation method (e.g., "Key
Identifier").
Change Controller:
For Standards Track RFCs, list the "IESG". 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 or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of
the documents. An indication of the relevant sections may also be
included but is not required.
6.2.2. Initial Registry Contents
o Confirmation Method Value: "jwk"
o Confirmation Method Description: JSON Web Key Representing Public
Key
o Change Controller: IESG
o Specification Document(s): Section 3.2 of [RFC7800]
o Confirmation Method Value: "jwe"
o Confirmation Method Description: Encrypted JSON Web Key
o Change Controller: IESG
o Specification Document(s): Section 3.3 of [RFC7800]
o Confirmation Method Value: "kid"
o Confirmation Method Description: Key Identifier
o Change Controller: IESG
o Specification Document(s): Section 3.4 of [RFC7800]
o Confirmation Method Value: "jku"
o Confirmation Method Description: JWK Set URL
o Change Controller: IESG
o Specification Document(s): Section 3.5 of [RFC7800]
7. References
7.1. Normative References
[IANA.JWT.Claims]
IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>.
[JWE] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7156, May 2015,
<http://www.rfc-editor.org/info/rfc7516>.
[JWK] Jones, M., "JSON Web Key (JWK)", RFC 7517,
DOI 10.17487/RFC7157, May 2015,
<http://www.rfc-editor.org/info/rfc7517>.
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7159, May 2015,
<http://www.rfc-editor.org/info/rfc7519>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
2003, <http://www.rfc-editor.org/info/rfc3629>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <http://www.rfc-editor.org/info/rfc6125>.
7.2. Informative References
[JWK.Thumbprint]
Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <http://www.rfc-editor.org/info/rfc7638>.
[OASIS.saml-core-2.0-os]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocol for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
2.0-os, March 2005,
<http://docs.oasis-open.org/security/saml/v2.0/>.
[OAUTH-POP-ARCH]
Hunt, P., Ed, Richer, J., Mills, W., Mishra, P., and H.
Tschofenig, "OAuth 2.0 Proof-of-Possession (PoP) Security
Architecture", Work in Progress, draft-ietf-oauth-pop-
architecture-07, December 2015.
[OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>.
Acknowledgements
The authors wish to thank Brian Campbell, Stephen Farrell, Barry
Leiba, Kepeng Li, Chris Lonvick, James Manger, Kathleen Moriarty,
Justin Richer, and Nat Sakimura for their reviews of the
specification.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
John Bradley
Ping Identity
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
Hannes Tschofenig
ARM Limited
Austria
Email: Hannes.Tschofenig@gmx.net
URI: http://www.tschofenig.priv.at