I just pushed some reorganization of the ecc code. It introduces an
internal struct ecc_modulo, which keeps the data and function pointers
needed for modulo p (or modulo q) arithmetic.
Immediate benefit was that a couple of wrapper functions could be
deleted. E.g, ecc_generic_modp and ecc_generic_modq both called ecc_mod,
but with different constants taken from different fields of struct
ecc_curve). Now, one can instead call ecc_mod (&ecc->p, ...) and
ecc_mod(&ecc->q, ...), respectively.
I also added an invert function pointer, and wrote a specialized modp
invert function for curve25519, which gives a nice little speedup. The
code can be shared with sqrt, since the main part of the addition chain
is the same for p-2 = 2^{255} - 21 (for invert) and (p-5)/8 = 2^{252} -
3 (for sqrt). Similar functions for the secp curves also make sense, at
least for the mod p inversion; modq is less structured.
The plan is to expand struct ecc_modulo with add, mul and sqr function
pointers, to make it possible to have a different internal
representation. In particular, using radix-51 for curve25519 modp
arithmetic, on 64-bit machines.
Regards,
/Niels
--
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
Internet email is subject to wholesale government surveillance.
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