FWIW, this all sounds reasonable to me, but it still sounds like trying to solve a problem that doesn't exist. The existing implementations use XEdDSA, and it's easy to get working in other libraries (they may even have the conversion function already, the rest is just convention and optional optimizations). Why in the world would we ask existing implementations to change for no benefit now that the only problem that the council raised before when accepting OMEMO is fixed and it's easy to make new implementations use the existing thing? If we ask existing implementations to change, all we're going to achieve is a fragmented ecosystem where half the OMEMO enabled clients don't work with the other half. I can imagine that sometimes this might be necessary, but I don't think it is in this case.
—Sam On Mon, May 29, 2017 at 12:53 AM, Remko Tronçon <[email protected]> wrote: > Hi, > > I may have a solution to our OMEMO key agreement discussion that satisfies > all of us. > > - We change the Identity keys to be Ed25519 keys instead of Curve25519. > Current client deployments are by default libsignal-based, and therefore > have access to Curve25519-to-Ed25519 conversion methods to convert already > authenticated keys, so they don't have to lose their keys. > - We change X3DH such that > - Sig(PK, M) is EdDSA(PK, M) instead of XEdDSA(PK, M) (PK is now an > Ed25519 key). Libsignal already comes with an Ed25519 implementation. > - DH(IK, ...) becomes DH(Ed2Curve(IK), ...). Ed25519-to-Curve25519 is a > conversion that is simpler than the other way round, and there are liberally > licensed implementations. Libsodium has a ref10-based one, so it can be > dropped in directly into libsignal: > https://download.libsodium.org/doc/advanced/ed25519-curve25519.html > > This drops the dependency on XEdDSA, and has a minimal impact on existing > libsignal-based implementations. It *does* make the key agreement more > complicated than the one in Olm (which does simple 3DH), but maybe that's a > price we're willing to pay? > > Remko > > _______________________________________________ > Standards mailing list > Info: https://mail.jabber.org/mailman/listinfo/standards > Unsubscribe: [email protected] > _______________________________________________ > -- Sam Whited pub 4096R/54083AE104EA7AD3 _______________________________________________ Standards mailing list Info: https://mail.jabber.org/mailman/listinfo/standards Unsubscribe: [email protected] _______________________________________________
