[CFRG] Re: Call for adoption: draft-google-cfrg-libzk-03 (Longfellow ZK)

[John Bradley <[e-mail]>]

I support adoption

> On Sep 30, 2026, at 10:56 AM, David Cook <dcook=[e-mail]> wrote:
> 
> I support adoption of this draft. I have previously reviewed earlier versions of the document, and helped implement a prior version with my colleagues at ISRG. I would be willing to review the document if it is adopted.
> 
> I had previously expressed hesitation about whether an IRTF RG was the appropriate venue for this work, but I trust the judgement of the authors and the chairs on this point. I am glad to see that the adoption call was made for this document, and not for the topic of zero knowledge proofs, or post-quantum secure zero knowledge proofs, as that allays my concerns. It's great to see this work moving forward, and to see more people contributing to it.
> --David Cook
> 
> On Fri, Sep 25, 2026 at 12:09 PM Nick Sullivan <[e-mail] <mailto:[e-mail]>> wrote:
>> Dear CFRG,
>> 
>> This message starts a two-week call for adoption of draft-google-cfrg-libzk-03, "Longfellow ZK", by Matteo Frigo and Abhi Shelat. The call ends on Friday October 9, 2026.
>> 
>> https://www.ietf.org/archive/id/draft-google-cfrg-libzk-03.html
>> 
>> The document specifies a post-quantum zero-knowledge argument system built to run on constrained devices while remaining expressive enough for real-world statements: ECDSA, SHA-256 and ML-DSA signature verification, string, integer and date comparisons, and basic parsing. Its Fiat-Shamir layer builds on the transformation the research group has already adopted, draft-irtf-cfrg-fiat-shamir-03.
>> 
>> The authors presented the work at IETF 122 through 125. The current revision has taken feedback from a large number of external reviewers, at least two independent groups have implemented it from the specification, and the authors have a Lean 4 formalization of the protocol and of the circuits for ECDSA verification and SHA-256, which they intend to release for external audit once internal review is done.
>> 
>> On relevance: drafts inside the IETF intend to build on this protocol, and outside the IETF it appears in eIDAS and EU age assurance documentation and is deployed in Google Wallet for digital identities and in India's UIDAI identity application.
>> 
>> Please reply on the list with whether you support adoption, and whether you would review or implement the document if it is adopted. Objections should name a specific problem with the document or with CFRG taking it on. Adoption means change control passes to the research group; the authors have indicated they are ready for that.
>> 
>> Thank you,
>> Nick, for the CFRG chairs
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