Re: [GNUnet-developers] EcDSA signature scheme

[Bernd Fix]

On 07/13/2018 04:50 PM, Christian Grothoff wrote:
> On 07/13/2018 06:39 PM, Bernd Fix wrote:
>> This constraint of course make things trickier, because that means we
>> are stuck in using Ed25519 for ECDHE. A possible solution (again: not
>> for GNUnet itself, but for implementators in general) for using Ed25519
>> points with ECDHE is to use the bijective mapping between Ed25519 and
>> Curve25519 and to do the ECDHE on Curve25519. Not nice probably, but
>> that could work.
> 
> Well, there is another possibility: simply have *two* versions of
> ECDHE/X25519: one for Taler where we mix it with EdDSA, and another one
> for GNUnet core/cadet KX where we do not rely on this property.

And maybe even a third one: I stumbled across an approach to use
Curve25519 keypairs for both ECDH and Ed25519 signatures
[https://moderncrypto.org/mail-archive/curves/2014/000293.html].

Would that be feasible also for Taler? Since Taler (afaik) relies on
some GNUnet mechanisms, it seems preferable not to introduce YACS (Yet
Another Crypto Scheme)...