Re: [GNUnet-developers] EdDSA signature process

[Christian Grothoff]

Filed as https://gnunet.org/bugs/view.php?id=5398

On 07/11/2018 02:58 PM, Bernd Fix wrote:
> The EdDSA signature implementation in GNUnet calls the 'gcry_pk_sign
> (&sig, msg, prv)' function not with the message itself, but with the
> SHA512 hash value of the message.
> 
> Due to the intricities of EdDSA signing this is not necessary (hashing
> is done in the sign function itself, as more than just the message is
> hashed for this).
> 
> Although the GNUnet approach is not breaking things technically, it
> produces unnecesary load: It is running an extra SHA512 - and because
> the signed message is usually rather small (from what I have seen until
> now the signed data is smaller than the 64 bytes of a SHA512 result),
> the sign functions even needs to hash more data than necessary.
> 
> I guess that changing the sign/verify procedure would break
> compatibility between new and old nodes and is therefore not feasable. I
> just want to mention this in case a major version change is considered.
> 
> Thanks for your attention, Bernd.
> 
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