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ed25519-donna: batch invert thing hopefully

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cathugger 2019-01-27 19:00:28 +02:00
parent f6138d29c4
commit f48239bbd7
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1 changed files with 40 additions and 0 deletions
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ed25519/ed25519-donna/curve25519-donna-helpers.h
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@ -48,6 +48,46 @@ curve25519_recip(bignum25519 out, const bignum25519 z) {
/* 2^255 - 21 */ curve25519_mul_noinline(out, b, a);
}
const static unsigned char curve25519_packedone[32] = {
1, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
};
static void
curve25519_setone(bignum25519 out) {
// (cathugger) this hopefuly will get inlined by compiler because im lazy
curve25519_expand(out, curve25519_packedone);
}
/*
* (cathugger)
* idk if recip is same as invert but I hope it is
* if that's the case then we're doing batch invert there
*/
static void
curve25519_batchrecip(bignum25519 *out[], bignum25519 tmp[], bignum25519 * const in[], size_t num) {
bignum25519 ALIGN(16) acc, tmpacc;
size_t i;
curve25519_setone(acc);
for (i = 0; i < num; ++i) {
curve25519_copy(tmp[i], acc);
curve25519_mul(acc, acc, *in[i]);
}
curve25519_recip(acc, acc);
i = num;
while (i--) {
curve25519_mul(tmpacc, acc, *in[i]);
curve25519_mul(*out[i], acc, tmp[i]);
curve25519_copy(acc, tmpacc);
}
}
/*
* z^((p-5)/8) = z^(2^252 - 3)
*/