29 Jul 16:51 2014

### curve25519 progress

I've now pushed some crude code (on the curve25519 branch) which agrees with the test vectors in draft-josefsson-tls-curve25519-05. It uses the equivalent Edwards curve for the internal operations. For scalar multiplication of the fix generator, it uses Pippenger's algorithm and tables very similar to the other curves, just with different point operations and no special caes (since the Edwards operations are "complete"). At the end, the x-coordinate of the corresponding point on the Montgomery-form curve25519 is computed. For scalar multiplication of an arbitrary point (with only x coordinate provided), I first have to compute the y-coordinate using Shanks-Tonelli (this could be used to implement "point compression") also for other curves). Then transform to a point on the Edwards curve, using homogeneneous/projective coordinates. Then the actual scalar multiply is currently done with the binary algorithm; I have code for window-based scalar multiply, but it needs a bit more debugging. All this is very similar to the other corves, but without special cases. Regards, /Niels -- -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.