Re: [Cfrg] request for comments: hashing to ristretto255
Filippo Valsorda <filippo@ml.filippo.io> Thu, 13 August 2020 06:05 UTC
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Date: Thu, 13 Aug 2020 02:04:00 -0400
From: Filippo Valsorda <filippo@ml.filippo.io>
To: cfrg@irtf.org
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Subject: Re: [Cfrg] request for comments: hashing to ristretto255
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2020-08-12 16:20 GMT-04:00 rsw@cs.stanford.edu: > Hello, > > I'm writing on behalf of the hash-to-curve authors to request feedback > on a proposed appendix for the hash-to-curve draft that specifies > a method for hashing to ristretto255. > > The proposed appendix is here: > https://github.com/cfrg/draft-irtf-cfrg-hash-to-curve/pull/294 > > The goal is to give a hash_to_ristretto255 function that is a drop-in > replacement for the hash_to_curve function, in the sense that it > gives the same API, the same security properties, and the same > domain separation strategy. This should make it easy for protocols > using a hash-to-curve function to migrate to ristretto255. > > (Note that hash_to_ristretto255 *does not* aim to return group elements > with any particular relationship to the ones returned by hash_to_curve > functions targeting curve25519 or edwards25519, as this would seemingly > violate the ristretto255 abstraction.) > > In more detail: the ristretto255 draft specifies a FROM_UNIFORM_BYTES > function that, on input a uniformly random 64-byte string, outputs > a random ristretto255 element. The hash_to_ristretto function simply > composes FROM_UNIFORM_BYTES with the same hashing primitives used > in the hash_to_curve function. > > Your feedback, by email or on GitHub, would be very much appreciated! Hello Riad, Thank you for working on this! Speaking for myself, this looks great judging from a quick skim, and I think it's a clean way to compose the h2c API and the r255 one. One quick note, the latest version of the ristretto255 draft did away with the eyesore FROM_UNIFORM_BYTES naming and just calls that function the one-way map. https://ietf.org/id/draft-irtf-cfrg-ristretto255-00.html#name-one-way-map Cheers, Filippo > Best regards, > > -=rsw > > _______________________________________________ > Cfrg mailing list > Cfrg@irtf.org > https://www.irtf.org/mailman/listinfo/cfrg >