| Internet-Draft | MoLE Protocols | June 2026 |
| Schlesinger | Expires 25 December 2026 | [Page] |
TODO Abstract¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://moderation-of-unlinkable-endorsements.github.io/internet-drafts/draft-schlesinger-mole-protocols.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-schlesinger-mole-protocols/.¶
Source for this draft and an issue tracker can be found at https://github.com/Moderation-of-unLinkable-Endorsements/internet-drafts.¶
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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 25 December 2026.¶
Copyright (c) 2026 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 (https://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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
In this document, we'll register all the token type that privacy pass is lacking and that we need. I suspect this is likely to lead to another registry, but maybe not needed.¶
We will NOT use the vocabulary from [RFC9576] but rather use [REVERSE-FLOW] vocabulary We indeed need to use credentialRequest/response and distinguish finalisation from presentation.¶
These are not specific to MoLE, but MoLE must constrain them.¶
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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
Unless otherwise specified, this document encodes protocol messages in TLS notation (Section 3 of [TLS13]). Moreover, all constants are in network byte order.¶
Beyond ACT (with some improvement), we'll need to specify the following protocol¶
Token type 0x0531¶
Configuration (these bits will probably differ for MoLE, and we should define the discovery we want)¶
Issuer Request URL <-- issuer name is going to be th erequest URL. Name is a footgun meant for private deployment¶
Issuer public key¶
Challenge value¶
Issuer set <-- magic crypto bits?¶
This token follws this flow with properties¶
how do we build context to get the endorsement¶
challenge?¶
presentation context: does it need to be flexible?¶
obtention of the issuer set from the origin: what information can the client validate to not reveal themselves¶
Note: this issuance protocol DOES NOT require a reverse flow, even if in MoLE it will use it to obtain a credential from an endorsement.¶
Realisation: there is work to do something like https://eprint.iacr.org/2026/870.pdf but without pairing¶
struct CredentialRequest {
uint16_t token_type = 0x0531; /* Type something(something) */
uint8_t truncated_token_key_id; /* Allow for multiple keys per issuer */
...
}
¶
struct CredentialResponse {
opaque response
}
¶
The client finalises the response into a Credential¶
struct Credential {
uint16_t token_type = 0x0531;
opaque cred
}
¶
The client knows the set of issuers it needs to present to. It presents the credential to obtain a token¶
struct Token {
uint16_t token_type = 0x0531;
opaque token
}
¶
We define a two round protocol between an Anchor and Client to produce an endorsement, and then a half-round Credential generation step presuming the Client knows the Anchors the Issuer accepts. We let hash2curve be the Hash2Curve function from [Hash2Curve], and H be hash function whose output length is sufficiently long.¶
The Endorsement is a structure with m, Y=Hash2Curve(m), Zhat, Xhat and private data gamma. The Anchor has a public key X and a private key x, and X = xG. The public form of a credential Zhat, Xhat, and a proof that Xhat = vG, Zhat = vY. Xhat = gamma X, and the client will prove it knows gamma such that Xhat is a power of one of the public keys of an Anchor the moderator trusts.¶
Client randomly selects scalars v and gamma, and sends Yprime = v Y to the anchor.¶
The Anchor computes Zprime = x Yprime, selects three random scalars aprime, bprime, and tprime. It computes a commitment. It then computes T1prime = tprime Yprime, T2Prime = tprime G. It then transmits Zprime, Cprime, and T1prime and T2prime to the client.¶
The client now has to compute some proof elements and send a scalar to the server. The client lets Zhat = gamma v^-1 Z. It then picks alpha, a random nonzero scalar, beta, a random scalar, epsilon, a random nonzero scalar, and rho, a random scalar. The client computes C = alpha^-1 C' - beta H, T1 = epsilon ^ -1 v ^ -1 (T1prime - rho Yprime), T2 = epsilon ^ -1 (T2prime - rho G).¶
The client now computes e = H(Y, Zhat, T1, T2, C), and sends eprime = epsilon alpha^{-1} gamma e to the anchor¶
The anchor computes rprime = tprime + eprime aprime x and sends back rprime aprime and bprime.¶
The client then checks Cprime = aprime G + bprime H, that aprime is invertable, and then computes a = alpha ^-1 aprime, b=alpha^-1 bprime - beta, r = epsilon ^ -1 (rprime - rho). The client then verifies Xhat, Zhat, m, e, a, b, r are a valid endorsement as in the section below.¶
A verifier gets Xhat, Zhat, m and e, a, b, r. The verifier computes Y=Hash2Curve(m), and then lets T1 = r Y - e a Zhat, T2 = rG - e a Xhat, C = a G + b H. It checks a is not zero and Y is not the identity and then checks e = H(Y, Zhat, T1, T2, C).¶
In addition to the above endorsement, the client must prove knowledge of a value gamma such that Xhat = gamma Xi for some i, where the Xi is the list of issuers trusted. This is a standard OR sigma proof, and we can use sigma stacking to compact the proof.¶
This document has no IANA actions.¶
TODO acknowledge.¶