RFC 8747

Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs)

📅 published March 2020, from ietf

📮 RFC 8747: Proof-of-Possession Key Semantics for CBOR Web Tokens (CWTs) 🦋

okay bestie, this one is SO my vibe 💖 it's a spec that lets a CBOR Web Token (CWT) say "hey, the person presenting me actually has a particular proof-of-possession key" 🔑✨ and that's what people call holder-of-key. it's giving the same energy as the JWT version (RFC 7800), just in CBOR and CWT form 🧚

Title block tea ☕🌈

Authors: M. Jones (Microsoft), L. Seitz (Combitech), G. Selander (Ericsson AB), S. Erdtman (Spotify), and H. Tschofenig (Arm Ltd.) 👑
Category: Standards Track, so this is an official Internet Standard 💅
Date: March 2020 📅
Obsoletes and updates: the header doesn't list either, so this doc doesn't replace or change any other RFCs 🙈
ISSN: 2070-1721 🌸

Status of This Memo ✨

okay so this is an Internet Standards Track doc 🎀 it came out of the IETF, it's got consensus from the community, it got public review, and the IESG approved it 💖 if you want to know more about Internet Standards, check out Section 2 of RFC 7841 📖 for the current status, errata, or to send feedback, head to https://www.rfc-editor.org/info/rfc8747 🦋

Copyright Notice 💅

Copyright (c) 2020 IETF Trust and the people listed as the document authors. All rights reserved 🌈 this doc is under BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) as of the publication date 📜 read those carefully, they tell you your rights and restrictions 🫶 and any Code Components pulled out of this doc have to include the Simplified BSD License text (Section 4.e of the Trust Legal Provisions) and come with no warranty, as the Simplified BSD License describes 💜

Table of Contents 🗺️

1.  Introduction
2.  Terminology
3.  Representations for Proof-of-Possession Keys
  3.1.  Confirmation Claim
  3.2.  Representation of an Asymmetric Proof-of-Possession Key
  3.3.  Representation of an Encrypted Symmetric
        Proof-of-Possession Key
  3.4.  Representation of a Key ID for a Proof-of-Possession Key
  3.5.  Specifics Intentionally Not Specified
4.  Security Considerations
5.  Privacy Considerations
6.  Operational Considerations
7.  IANA Considerations
  7.1.  CBOR Web Token Claims Registration
    7.1.1.  Registry Contents
  7.2.  CWT Confirmation Methods Registry
    7.2.1.  Registration Template
    7.2.2.  Initial Registry Contents
8.  References
  8.1.  Normative References
  8.2.  Informative References
Acknowledgements
Authors' Addresses

1. Introduction 🌸

okay so this spec describes how a CBOR Web Token (CWT) [RFC8392] can declare that the presenter of the CWT has a particular proof-of-possession (PoP) key 🔑 proof of possession is also called holder-of-key, same thing 💅 it gives you the same functionality as "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)" [RFC7800], but it uses Concise Binary Object Representation (CBOR) [RFC7049] and CWTs [RFC8392] instead of JavaScript Object Notation (JSON) [RFC8259] and JSON Web Tokens (JWTs) [JWT] 🧚✨

2. Terminology 🎀

the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this doc are to be read as described in BCP 14 [RFC2119] [RFC8174], but only when they show up in all capitals like this 🫶 lowercase ones are just regular words, no cap 💀

this spec uses terms from the CBOR Web Token (CWT) [RFC8392], CBOR Object Signing and Encryption (COSE) [RFC8152], and Concise Binary Object Representation (CBOR) [RFC7049] specs 📚

these terms get defined in this spec too 💜

Issuer the party that creates the CWT and binds the claims about the subject to the proof-of-possession key 👑

Presenter the party that proves it has a private key (asymmetric crypto) or a secret key (symmetric crypto) to a recipient of a CWT 🦋

in OAuth, this party is also called the OAuth Client 💅

Recipient the party that receives the CWT with the proof-of-possession key info from the presenter 🌈

in OAuth, this party is also called the OAuth Resource Server 🫶

this spec gives examples in CBOR extended diagnostic notation, as defined in Appendix G of [RFC8610] 🍓 the examples have line breaks so they're easier to read ✨

3. Representations for Proof-of-Possession Keys 🔑

okay so by including a "cnf" (confirmation) claim in a CWT, the issuer of the CWT declares that the presenter has a particular key, and that the recipient can cryptographically confirm the presenter really has it 🔐 the value of "cnf" is a CBOR map (defined in Section 2.1 of [RFC7049]), and the members of that map identify the proof-of-possession key 💖

the CWT can identify the presenter in a few different ways, depending on what the application needs 🧚 for example, some apps use the CWT "sub" (subject) claim [RFC8392] to identify the presenter, and others use the "iss" (issuer) claim [RFC8392] 🌸 in some apps, the subject identifier is relative to the issuer named by the "iss" claim 🦋 which mechanism gets used depends on the application 💅 when the presenter is the subject of the CWT, it's analogous to the SAML 2.0 [OASIS.saml-core-2.0-os] SubjectConfirmation usage 👑

3.1. Confirmation Claim 🎀

the "cnf" claim in the CWT carries confirmation methods 💜 some of them use proof-of-possession keys and some don't 🌈 this design is analogous to the SAML 2.0 [OASIS.saml-core-2.0-os] SubjectConfirmation element, which can include a bunch of different subject confirmation methods (including proof-of-possession key info) 🫶

the set of confirmation members a CWT MUST contain to be considered valid depends on context and is outside the scope of this spec 💀 specific applications will need implementations to understand and process some confirmation members in particular ways 🍓 but if there are no such requirements, all confirmation members that implementations don't understand MUST be ignored 🙈

Section 7.2 sets up the IANA "CWT Confirmation Methods" registry for CWT "cnf" member values and registers the members defined by this spec ✨ other specs can register other members for confirmation, including ones that carry proof-of-possession keys in different key representations 🦋

the "cnf" claim value MUST represent only a single proof-of-possession key 👑 at most one of the "COSE_Key" and "Encrypted_COSE_Key" confirmation values defined in Table 1 MAY be present 💅 note that if an app needs to represent multiple proof-of-possession keys in the same CWT, one way to do it is to use other claim names (in addition to "cnf") to hold the extra key info 🧚 those claims can use the same syntax and semantics as "cnf" 🌸 they'd be defined by apps or other specs and could be registered in the IANA "CBOR Web Token (CWT) Claims" registry [IANA.CWT.Claims] 🎀

    +--------------------+-----+-------------------------------+
    | Name               | Key | Value type                    |
    +====================+=====+===============================+
    | COSE_Key           | 1   | COSE_Key                      |
    +--------------------+-----+-------------------------------+
    | Encrypted_COSE_Key | 2   | COSE_Encrypt or COSE_Encrypt0 |
    +--------------------+-----+-------------------------------+
    | kid                | 3   | binary string                 |
    +--------------------+-----+-------------------------------+

     Table 1: Summary of the "cnf" Names, Keys, and Value Types

3.2. Representation of an Asymmetric Proof-of-Possession Key 🔐

when the key the presenter holds is an asymmetric private key, the "COSE_Key" member is a COSE_Key [RFC8152] representing the matching asymmetric public key 🦋 here's an example of that declaration in the CWT Claims Set of a CWT ✨

  {
  /iss/ 1 : "coaps://server.example.com",
  /aud/ 3 : "coaps://client.example.org",
  /exp/ 4 : 1879067471,
  /cnf/ 8 :{
    /COSE_Key/ 1 :{
      /kty/ 1 : /EC2/ 2,
      /crv/ -1 : /P-256/ 1,
      /x/ -2 : h'd7cc072de2205bdc1537a543d53c60a6acb62eccd890c7fa27c9
                 e354089bbe13',
      /y/ -3 : h'f95e1d4b851a2cc80fff87d8e23f22afb725d535e515d020731e
                 79a3b4e47120'
     }
   }
 }

the COSE_Key MUST contain the required key members for a COSE_Key of that key type 💅 it MAY also contain other COSE_Key members, including the "kid" (Key ID) member 🌈

the "COSE_Key" member MAY also be used for a COSE_Key representing a symmetric key, but only if the CWT is encrypted so the key isn't revealed to unintended parties 🫶 the way to encrypt a CWT is explained in [RFC8392] 🍓 if the CWT is NOT encrypted, the symmetric key MUST be encrypted as described in Section 3.3 💀 this procedure is equivalent to the one defined in Section 3.3 of [RFC7800] 🦋

okay that's part 1 done 💖 more parts are coming, so stay tuned bestie 🧚✨

3.3. Representation of an Encrypted Symmetric Proof-of-Possession Key 🔐

Okay so, when the key the presenter holds is a symmetric key, the "Encrypted_COSE_Key" member is an encrypted COSE_Key [RFC8152] that represents that symmetric key. The symmetric key is encrypted to a key the recipient knows, using COSE_Encrypt or COSE_Encrypt0. It's giving secret-keeper energy 🤫💜

Here's a symmetric key that could later get encrypted for the "Encrypted_COSE_Key" member:

{
 /kty/ 1 : /Symmetric/ 4,
 /alg/ 3 : /HMAC 256-256/ 5,
 /k/ -1 : h'6684523ab17337f173500e5728c628547cb37df
            e68449c65f885d1b73b49eae1'
}

The COSE_Key representation is what gets used as the plaintext when encrypting the key. ✨

Next, here's a CWT Claims Set showing an encrypted symmetric key used as the "Encrypted_COSE_Key" member value. Obsessed with how neat this is 🎀

{
 /iss/ 1 : "coaps://server.example.com",
 /sub/ 2 : "24400320",
 /aud/ 3: "s6BhdRkqt3",
 /exp/ 4 : 1311281970,
 /iat/ 5 : 1311280970,
 /cnf/ 8 : {
 /Encrypted_COSE_Key/ 2 : [
    /protected header/ h'A1010A' /{ \alg\ 1:10 \AES-CCM-16-64-128\}/,
    /unprotected header/ { / iv / 5: h'636898994FF0EC7BFCF6D3F95B'},
    /ciphertext/  h'0573318A3573EB983E55A7C2F06CADD0796C9E584F1D0E3E
                    A8C5B052592A8B2694BE9654F0431F38D5BBC8049FA7F13F'
   ]
  }
}

The example above was generated with this key: h'6162630405060708090a0b0c0d0e0f10' 🌸

3.4. Representation of a Key ID for a Proof-of-Possession Key 🪪

The proof-of-possession key can also be identified with a Key ID instead of sending the actual key, as long as the recipient can obtain the identified key using that Key ID. In this case, the issuer of a CWT says the presenter has a particular key, and the recipient can cryptographically confirm the presenter's proof of possession by putting a "cnf" claim in the CWT. That claim's value is a CBOR map with a "kid" member that identifies the key. This is so clean 😭

Here's what that declaration looks like in the CWT Claims Set:

{
 /iss/ 1 : "coaps://as.example.com",
 /aud/ 3 : "coaps://resource.example.org",
 /exp/ 4 : 1361398824,
 /cnf/ 8 : {
   /kid/ 3 : h'dfd1aa976d8d4575a0fe34b96de2bfad'
  }
}

The content of the "kid" value is application specific. For instance, some applications may choose to use a cryptographic hash of the public key value as the "kid" value. 🧩

Heads up, bestie! Using a Key ID to identify a proof-of-possession key needs to be carefully circumscribed, as described below and in Section 6. If the Key ID isn't a cryptographic value derived from the key, or not all of the parties are validating that derivation, implementers should expect collisions where different keys get the same Key ID. Recipients of a CWT with a PoP key linked only through a Key ID should be prepared to handle that mess. 💀

In the world of constrained Internet of Things (IoT) devices, there's frequently a limit on the size of Key IDs, either because of table constraints or a desire to keep message sizes small. 🌱

Also, the value of a Key ID for a specific key isn't necessarily the same for different parties. When sending a COSE encrypted message with a shared key, the Key ID may be different on both sides of the conversation. The right one gets included in the message based on who the recipient is. 🦋

3.5. Specifics Intentionally Not Specified 🤷‍♀️

Proof of possession is often shown by having the presenter sign a value that the recipient picks, using the key the presenter holds. This value is sometimes called a "nonce" or a "challenge". There are also other ways to show that the exchange is fresh and to link the proof-of-possession key to the parties involved, as different authentication and key exchange protocols demonstrate. 🔑

The way the nonce gets communicated, and what its contents look like, are intentionally not described in this specification, because different protocols communicate that info in different ways. The way the signed nonce gets communicated isn't specified either, since that's protocol specific too. 📬

Other means of proving possession of the key exist, and they could be used together with a CWT's confirmation key. Applications using those alternate means are encouraged to register them in the IANA "CBOR Web Token (CWT) Confirmation Methods" registry established in Section 7.2. 🌈

4. Security Considerations 🚨

All the security considerations discussed in [RFC8392] also apply here. On top of that, proof of possession brings its own unique security issues. Possessing a key is only valuable if it stays secret, so appropriate means have to be used to make sure unintended parties don't learn private key or symmetric key values. 🙈

Applications utilizing proof of possession SHOULD also utilize audience restriction, as described in Section 3.1.3 of [RFC8392], because it provides additional protections. Audience restriction can be used by recipients to reject messages intended for different recipients. (Of course, applications not using proof of possession can also benefit from using audience restriction to reject messages meant for different recipients. 💅)

CBOR Web Tokens with proof-of-possession keys get used within an architecture, such as the ACE OAuth Framework [ACE-OAUTH]. In that setup, protocols are used by a presenter to request these tokens and then use them with recipients. Proof of possession only gives the intended security gains when the proof is known to be current and not subject to replay attacks. Security protocols using mechanisms such as nonces and timestamps can be used to avoid the risk of replay when doing proof of possession for a token. The architecture and the specific protocols CWTs with proof-of-possession keys are used with are beyond the scope of this specification, so that's a whole other conversation 🧚

As with any other information included in a CWT, it's necessary to apply data origin authentication and integrity protection (via a keyed message digest or a digital signature). Data origin authentication makes sure the recipient of the CWT learns about the entity that created it, which matters a lot for policy decisions. Integrity protection stops an adversary from changing any elements conveyed within the CWT payload. Special care has to be applied when carrying symmetric keys inside the CWT, since those need integrity protection and confidentiality protection. 😤

As described in Section 6 (Key Identification) and Appendix D (Notes on Key Selection) of [JWS], it's important to make explicit trust decisions about the keys. Proof-of-possession signatures made with keys that don't meet the application's trust criteria MUST NOT be relied upon. 🛑

5. Privacy Considerations 🫣

A proof-of-possession key can be used as a correlation handle if the same key is used on multiple occasions. So, for privacy reasons, it is recommended that different proof-of-possession keys be used when interacting with different parties. Main character energy means never leaving a trail 👑

6. Operational Considerations 🛠️

Using CWTs with proof-of-possession keys requires extra info to be shared between the involved parties so everything gets processed correctly. The recipient needs to be able to use credentials to verify the authenticity and integrity of the CWT. The recipient may also need to decrypt either the whole CWT or its encrypted parts (see Section 3.3), which means it has to know info about the issuer. And there needs to be agreement between the issuer and the recipient about the claims being used (which is also true of CWTs in general). 🤝

When an issuer creates a CWT containing a Key ID claim, it needs to make sure it doesn't issue another CWT with different claims containing the same Key ID within the lifetime of the CWTs, unless that's intentionally desired. 🚫 If it does, one party might impersonate another party and gain additional privileges. Scary stuff 😱

A case where reusing a Key ID is intentional: a presenter gets a CWT with different claims (e.g., extended scope) for the same recipient, but wants to keep using an existing security association (e.g., a DTLS session) bound to the key identified by the Key ID. 🔁

Also, if PoP keys are used for multiple different kinds of CWTs in an application and those keys are identified by Key IDs, care must be taken to keep the keys for the different kinds of CWTs segregated. That way an attacker can't cause the wrong PoP key to be used by presenting a valid Key ID for the wrong kind of CWT. Using an audience restriction for the CWT would be one strategy to mitigate this risk. 🧱

7. IANA Considerations 📚

The following registration procedure is used for all the registries established by this specification. 📝

Values are registered on a Specification Required [RFC8126] basis, after a three-week review period on the <cwt-reg-review@ietf.org> mailing list, on the advice of one or more designated experts. However, to allow values to be allocated before publication, the designated experts may approve a registration once they're 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 CWT Confirmation Method: example"). Registration requests that are undetermined for a period longer than 21 days can be brought directly to IANA's attention (using the iana@iana.org mailing list) for resolution. ⏰

Designated experts should determine whether a registration request contains enough info for the registry to be populated with the new values, and whether the proposed new functionality already exists. If a registration is incomplete, or it tries to register functionality that already exists, the designated experts should ask for corrections or reject the registration. 🙅‍♀️

It's suggested that multiple designated experts be appointed who can represent the perspectives of the different applications using this specification. That way the review of registration decisions is broadly informed. If a registration decision could be seen as creating a conflict of interest for a particular expert, that expert should defer to the judgment of the other experts. 🫶

7.1. CBOR Web Token Claims Registration 🏷️

This specification registers the "cnf" claim in the IANA "CBOR Web Token (CWT) Claims" registry [IANA.CWT.Claims], which was established by [RFC8392].

7.1.1. Registry Contents 📋

Claim Name: "cnf"
Claim Description: Confirmation
JWT Claim Name: "cnf"
Claim Key: 8
Claim Value Type(s): map
Change Controller: IESG
Specification Document(s): Section 3.1 of RFC 8747

7.2. CWT Confirmation Methods Registry 🗂️

This specification establishes the IANA "CWT Confirmation Methods" registry for CWT "cnf" member values. The registry records the confirmation method member and a reference to the specification that defines it. 💖

7.2.1. Registration Template ✨

okay bestie, this is the form you fill out to add a new confirmation method 📋🎀

Confirmation Method Name: the human-readable name you're asking for, like "kid" 🏷️
Confirmation Method Description: a quick blurb about the method, like "Key Identifier" 💅
JWT Confirmation Method Name: the Claim Name of the matching JWT confirmation method value, as registered in the "JSON Web Token Claims" subregistry in the "JSON Web Token (JWT)" registry [IANA.JWT]. CWT claims should normally have a corresponding JWT claim 🦋 If a corresponding JWT claim would not make sense, the designated experts can choose to accept registrations where the JWT Claim Name is listed as "N/A" 🤷‍♀️
Confirmation Key: the CBOR map key value for the confirmation method 🔑
Confirmation Value Type(s): the CBOR types that can be used for the confirmation method value 🧩
Change Controller: for Standards Track RFCs, list the "IESG". For everything else, give the name of the responsible party 👑
Specification Document(s): a reference to the document or documents that specify the parameter, ideally with URIs where people can grab copies 📚 You can also point to the relevant sections, but that's optional 💜 Note that the designated experts and IANA must be able to obtain copies of the specification document(s) so they can do their work 🫶

7.2.2. Initial Registry Contents 🌈

these are the three entries that start off the registry, and they're giving main character energy 👑

Confirmation Method Name: "COSE_Key"
Confirmation Method Description: COSE_Key Representing Public Key
JWT Confirmation Method Name: "jwk"
Confirmation Key: 1
Confirmation Value Type(s): COSE_Key structure
Change Controller: IESG
Specification Document(s): Section 3.2 of RFC 8747 🔐
Confirmation Method Name: "Encrypted_COSE_Key"
Confirmation Method Description: Encrypted COSE_Key
JWT Confirmation Method Name: "jwe"
Confirmation Key: 2
Confirmation Value Type(s): COSE_Encrypt or COSE_Encrypt0 structure (with an optional corresponding COSE_Encrypt or COSE_Encrypt0 tag)
Change Controller: IESG
Specification Document(s): Section 3.3 of RFC 8747 🫧
Confirmation Method Name: "kid"
Confirmation Method Description: Key Identifier
JWT Confirmation Method Name: "kid"
Confirmation Key: 3
Confirmation Value Type(s): binary string
Change Controller: IESG
Specification Document(s): Section 3.4 of RFC 8747 🍓

8. References ✨

8.1. Normative References 📖

[IANA.CWT.Claims] IANA, "CBOR Web Token Claims", <https://www.iana.org/assignments/cwt>.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.

[RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, <https://www.rfc-editor.org/info/rfc7049>.

[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>.

[RFC8152] Schaad, J., "CBOR Object Signing and Encryption (COSE)", RFC 8152, DOI 10.17487/RFC8152, July 2017, <https://www.rfc-editor.org/info/rfc8152>.

[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.

[RFC8392] Jones, M., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "CBOR Web Token (CWT)", RFC 8392, DOI 10.17487/RFC8392, May 2018, <https://www.rfc-editor.org/info/rfc8392>.

8.2. Informative References 🫧

[ACE-OAUTH] Seitz, L., Selander, G., Wahlstroem, E., Erdtman, S., and H. Tschofenig, "Authentication and Authorization for Constrained Environments (ACE) using the OAuth 2.0 Framework (ACE-OAuth)", Work in Progress, Internet-Draft, draft-ietf-ace-oauth-authz-21, 14 February 2019, <https://tools.ietf.org/html/draft-ietf-ace-oauth-authz-21>.

[IANA.JWT] IANA, "JSON Web Token (JWT)", <https://www.iana.org/assignments/jwt>.

[JWS] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, <https://www.rfc-editor.org/info/rfc7515>.

[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, <https://www.rfc-editor.org/info/rfc7519>.

[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, <https://docs.oasis-open.org/security/saml/v2.0/saml-core-2.0-os.pdf>.

[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)", RFC 7800, DOI 10.17487/RFC7800, April 2016, <https://www.rfc-editor.org/info/rfc7800>.

[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data Interchange Format", STD 90, RFC 8259, DOI 10.17487/RFC8259, December 2017, <https://www.rfc-editor.org/info/rfc8259>.

[RFC8610] Birkholz, H., Vigano, C., and C. Bormann, "Concise Data Definition Language (CDDL): A Notational Convention to Express Concise Binary Object Representation (CBOR) and JSON Data Structures", RFC 8610, DOI 10.17487/RFC8610, June 2019, <https://www.rfc-editor.org/info/rfc8610>.

Acknowledgements 💖

Huge thanks to the following people for their reviews of the specification: Roman Danyliw, Christer Holmberg, Benjamin Kaduk, Mirja Kühlewind, Yoav Nir, Michael Richardson, Adam Roach, Éric Vyncke, and Jim Schaad 🙌

Ludwig Seitz and Göran Selander worked on this document as part of the CelticPlus projects CyberWI and CRITISEC, with funding from Vinnova 🇸🇪🌸

Authors' Addresses 🧚

Michael B. Jones
Microsoft

Email: mbj@microsoft.com
URI:   https://self-issued.info/

Ludwig Seitz
Combitech
Djaeknegatan 31
SE-211 35 Malmö
Sweden

Email: ludwig.seitz@combitech.se

Göran Selander
Ericsson AB
SE-164 80 Kista
Sweden

Email: goran.selander@ericsson.com

Samuel Erdtman
Spotify

Email: erdtman@spotify.com

Hannes Tschofenig
Arm Ltd.
6060 Hall in Tirol
Austria

Email: Hannes.Tschofenig@arm.com

📦 where this page comes from

ietf: rfc8747 2020-03
💖 girlified by claude-haiku-5-5 on 2026-10-18: a language model's rewrite of the original, under its terms