JWK Thumbprint URI Microsoft
mbj@microsoft.com https://self-issued.info/
Microsoft
kryasuda@microsoft.com https://twitter.com/kristinayasuda
Security OAuth JSON Web Key JWK Thumbprint URI URN OAuth This specification registers a kind of URI that represents a JSON Web Key (JWK) Thumbprint value. JWK Thumbprints are defined in RFC 7638. This enables JWK Thumbprints to be used, for instance, as key identifiers in contexts requiring URIs.
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 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at .
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Table of Contents
  • .  Introduction
  • .  Requirements Notation and Conventions
  • .  JWK Thumbprint URI
  • .  Hash Algorithms Identifier
  • .  Mandatory to Implement Hash Algorithm
  • .  Example JWK Thumbprint URI
  • .  Security Considerations
    • .  Multiple Public Keys per Private Key
  • .  IANA Considerations
    • .  OAuth URI Registration
      • .  Registry Contents
  • .  References
    • .  Normative References
    • .  Informative References
  • Acknowledgements
  • Authors' Addresses
Introduction A JSON Web Key (JWK) Thumbprint is a URL-safe representation of a hash value over a JWK . This specification defines a URI prefix indicating that the portion of the URI following the prefix is a JWK Thumbprint. This enables JWK Thumbprints to be communicated in contexts requiring URIs, including in specific JSON Web Token (JWT) claims. JWK Thumbprint URIs are being used in the specification as one kind of subject identifier in a context requiring that the identifier be a URI. In this case, the subject identifier is derived from a public key represented as a JWK. Expressing the identifier as a JWK Thumbprint URI enables this kind of identifier to be differentiated from other kinds of identifiers that are also URIs, such as Decentralized Identifiers (DIDs) .
Requirements Notation and 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 BCP 14 when, and only when, they appear in all capitals, as shown here.
JWK Thumbprint URI The following URI prefix is defined to indicate that the portion of the URI following the prefix is a JWK Thumbprint: urn:ietf:params:oauth:jwk-thumbprint To make the hash algorithm being used explicit in a URI, the prefix is followed by a hash algorithm identifier and a JWK Thumbprint value, each separated by a colon character to form a URI representing a JWK Thumbprint.
Hash Algorithms Identifier Hash algorithm identifiers used in JWK Thumbprint URIs MUST be values from the "Hash Name String" column in the IANA "Named Information Hash Algorithm Registry" . JWK Thumbprint URIs with hash algorithm identifiers not found in this registry are not considered valid and applications will need to detect and handle this error, should it occur.
Mandatory to Implement Hash Algorithm To promote interoperability among implementations, the SHA-256 hash algorithm is mandatory to implement.
Example JWK Thumbprint URI contains the following example JWK Thumbprint value: NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs A complete JWK Thumbprint URI using the above JWK Thumbprint and SHA-256 hash algorithm is as follows: urn:ietf:params:oauth:jwk-thumbprint:sha-256:NzbLsXh8uDCcd-6MNwXF4W_7noWXFZAfHkxZsRGC9Xs
Security Considerations The security considerations of also apply when using this specification.
Multiple Public Keys per Private Key There are cryptographic algorithms for which multiple public keys correspond to the same private key. This is described in the security considerations of as follows:
Designers using these curves should be aware that for each public key, there are several publicly computable public keys that are equivalent to it, i.e., they produce the same shared secrets. Thus using a public key as an identifier and knowledge of a shared secret as proof of ownership (without including the public keys in the key derivation) might lead to subtle vulnerabilities.
This consideration for public keys as identifiers equally applies to JWK Thumbprint URIs used as identifiers. A recommended way to ensure that the JWK Thumbprint URI corresponds to the actual public key used is to sign a message containing the correct public key with the private key. This signed message could also contain the JWK Thumbprint URI (although, by definition, it could also be computed directly from the public key).
IANA Considerations
OAuth URI Registration This specification registers the following value in the IANA "OAuth URI" registry established by .
Registry Contents
URN:
urn:ietf:params:oauth:jwk-thumbprint
Common Name:
JWK Thumbprint URI
Change controller:
IESG
Specification Document:
RFC 9278
 References Normative References OAuth Parameters IANA Key words for use in RFCs to Indicate Requirement Levels In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. JSON Web Key (JWK) Thumbprint This specification defines a method for computing a hash value over a JSON Web Key (JWK). It defines which fields in a JWK are used in the hash computation, the method of creating a canonical form for those fields, and how to convert the resulting Unicode string into a byte sequence to be hashed. The resulting hash value can be used for identifying or selecting the key represented by the JWK that is the subject of the thumbprint. Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References Decentralized Identifiers (DIDs) v1.0 Digital Bazaar Digital Bazaar Danube Tech Evernym Named Information Hash Algorithm Registry IANA An IETF URN Sub-Namespace for OAuth This document establishes an IETF URN Sub-namespace for use with OAuth-related specifications. This document is not an Internet Standards Track specification; it is published for informational purposes. JSON Web Key (JWK) A JSON Web Key (JWK) is a JavaScript Object Notation (JSON) data structure that represents a cryptographic key. This specification also defines a JWK Set JSON data structure that represents a set of JWKs. Cryptographic algorithms and identifiers for use with this specification are described in the separate JSON Web Algorithms (JWA) specification and IANA registries established by that specification. JSON Web Token (JWT) JSON Web Token (JWT) is a compact, URL-safe means of representing claims to be transferred between two parties. The claims in a JWT are encoded as a JSON object that is used as the payload of a JSON Web Signature (JWS) structure or as the plaintext of a JSON Web Encryption (JWE) structure, enabling the claims to be digitally signed or integrity protected with a Message Authentication Code (MAC) and/or encrypted. Elliptic Curves for Security This memo specifies two elliptic curves over prime fields that offer a high level of practical security in cryptographic applications, including Transport Layer Security (TLS). These curves are intended to operate at the ~128-bit and ~224-bit security level, respectively, and are generated deterministically based on a list of required properties. Self-Issued OpenID Provider v2 Microsoft Microsoft yes.com
Acknowledgements Use cases for this specification were developed in the OpenID Connect Working Group of the OpenID Foundation. Specifically, it is being used as a key identifier in the specification. The following individuals also contributed to the creation of this specification: , , , , , , , , , , , , , , , , , and .
Authors' Addresses Microsoft
mbj@microsoft.com https://self-issued.info/
Microsoft
kryasuda@microsoft.com https://twitter.com/kristinayasuda