triple DH

[Christian Grothoff]

On 05/21/2015 11:17 AM, Werner Koch wrote:
> On Wed, 20 May 2015 12:41, wk at gnupg.org said:
>
>> Thus this is about generating keys in a way to allow point compression
>> in a non-patent encumbered way.  Meanwhile the point compression patent
> The reason for the lower speed can not be attributed to Jivsov's trick
> but the fact that we convert to affine coordinates twice (which requires
> an inversion).  The attached patch remove the double conversion.
>
> Does this help?
>
>
Short answer: no.

Long answer: Measurements show that for

ECDHE nist_generate_key() calls 38x gcry_mpi_ec_mul_point via
_gcry_ecc_ecdsa_sign and 77x via gcry_ecc_ecdsa_verify and 38x via
gcry_ecc_eddsa_genkey

while for

EdDSA nist_generate_key() calls 12x gcry_mpi_ec_mul_point via
_gcry_ecc_ecdsa_sign and 23x via gcry_ecc_ecdsa_verify, and 12x via
gcry_ecc_eddsa_genkey

Detailed measurement plots were too big for the list (> 40k).

-Christian

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