triple DH

[Werner Koch]

On Tue, 19 May 2015 13:56, christian at grothoff.org said:

> Why is this? In ecc.c:158, we see that
>
>  if (E->dialect == ECC_DIALECT_ED25519)
>     point_set (&sk->Q, &Q);
>   else
>     {
>     // ... lots of code
>     }
>
> the key generation logic diverges here.  The reason is that for NIST
> curves (and other non-Curve25519)

The comment a few lines above explains it:

  /* We want the Q=(x,y) be a "compliant key" in terms of the
   * http://tools.ietf.org/html/draft-jivsov-ecc-compact, which simply
   * means that we choose either Q=(x,y) or -Q=(x,p-y) such that we

Thus this is about generating keys in a way to allow point compression
in a non-patent encumbered way.  Meanwhile the point compression patent
expired and thus this does not make much sense anymore.  I'll ask Andrey
Jivsov on how we can proceed here.


Salam-Shalom,

   Werner

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