[CFRG] Re: Adoption Call: Partially Blind RSA Signatures

[Kevin Yeo <[e-mail]>]

Hi Chris,

This particular protocol was chosen as it is a two-move, pairing-free
partially blind signature. Two-move protocols enable each blind signing
protocol to be executed in a single roundtrip between the user and signer.

In contrast, the partially blind signatures that you linked (Tessaro-Zhu
and Kastner-Loss-Xu) are both three-move protocols. In practice, this means
that the blind signing protocol requires two rounds between the user and
signer that may be prohibitive in many applications.

One more reason that two-move protocols are more desirable is that their
security is the same in both the sequential and concurrent models (this is
known to be false for three-move protocols). See
https://eprint.iacr.org/2022/895.pdf for further details on concurrent
security for two-move blind signatures.

Best,
Kevin

On Wed, Aug 21, 2024 at 1:03 PM Chris Barber <[e-mail]> wrote:

> Hi everyone,
>
> I’m curious why we should adopt this particular protocol, and whether
> moving away from RSA might be a better path forward for new protocols.
>
> The Tessaro-Zhu [1] and Kaster-Loss-Rosenberg-Xu [2] protocols are more
> efficient, and the concurrency concerns in the Abe–Okamoto protocol could
> likely be addressed.
>
> [1] https://eprint.iacr.org/2022/047
> [2] https://eprint.iacr.org/2020/1071
>
> On Fri, Aug 16, 2024 at 11:24 AM Stanislav V. Smyshlyaev <
> [e-mail]> wrote:
>
>> Dear CFRG participants,
>>
>> This message is starting 3 weeks adoption call on "Partially Blind RSA
>> Signatures" draft, draft-amjad-cfrg-partially-blind-rsa (
>> https://datatracker.ietf.org/doc/draft-amjad-cfrg-partially-blind-rsa/)
>> that will end on September 6th 2024.
>>
>> Please send your feedback in reply to this email or directly to CFRG
>> chairs <[e-mail]> <[e-mail]>.
>>
>> Best regards,
>> Stanislav (for CFRG chairs)
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