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https://github.com/cathugger/mkp224o.git
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115 lines
3.6 KiB
C
115 lines
3.6 KiB
C
/*
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Public domain by Andrew M. <liquidsun@gmail.com>
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See: https://github.com/floodyberry/curve25519-donna
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Curve25519 implementation agnostic helpers
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*/
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/*
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* In: b = 2^5 - 2^0
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* Out: b = 2^250 - 2^0
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*/
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static void
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curve25519_pow_two5mtwo0_two250mtwo0(bignum25519 b) {
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bignum25519 ALIGN(16) t0,c;
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/* 2^5 - 2^0 */ /* b */
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/* 2^10 - 2^5 */ curve25519_square_times(t0, b, 5);
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/* 2^10 - 2^0 */ curve25519_mul_noinline(b, t0, b);
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/* 2^20 - 2^10 */ curve25519_square_times(t0, b, 10);
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/* 2^20 - 2^0 */ curve25519_mul_noinline(c, t0, b);
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/* 2^40 - 2^20 */ curve25519_square_times(t0, c, 20);
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/* 2^40 - 2^0 */ curve25519_mul_noinline(t0, t0, c);
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/* 2^50 - 2^10 */ curve25519_square_times(t0, t0, 10);
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/* 2^50 - 2^0 */ curve25519_mul_noinline(b, t0, b);
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/* 2^100 - 2^50 */ curve25519_square_times(t0, b, 50);
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/* 2^100 - 2^0 */ curve25519_mul_noinline(c, t0, b);
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/* 2^200 - 2^100 */ curve25519_square_times(t0, c, 100);
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/* 2^200 - 2^0 */ curve25519_mul_noinline(t0, t0, c);
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/* 2^250 - 2^50 */ curve25519_square_times(t0, t0, 50);
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/* 2^250 - 2^0 */ curve25519_mul_noinline(b, t0, b);
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}
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/*
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* z^(p - 2) = z(2^255 - 21)
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*/
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static void
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curve25519_recip(bignum25519 out, const bignum25519 z) {
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bignum25519 ALIGN(16) a,t0,b;
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/* 2 */ curve25519_square_times(a, z, 1); /* a = 2 */
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/* 8 */ curve25519_square_times(t0, a, 2);
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/* 9 */ curve25519_mul_noinline(b, t0, z); /* b = 9 */
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/* 11 */ curve25519_mul_noinline(a, b, a); /* a = 11 */
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/* 22 */ curve25519_square_times(t0, a, 1);
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/* 2^5 - 2^0 = 31 */ curve25519_mul_noinline(b, t0, b);
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/* 2^250 - 2^0 */ curve25519_pow_two5mtwo0_two250mtwo0(b);
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/* 2^255 - 2^5 */ curve25519_square_times(b, b, 5);
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/* 2^255 - 21 */ curve25519_mul_noinline(out, b, a);
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}
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static const unsigned char curve25519_packedone[32] = {
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1, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0,
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};
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static void
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curve25519_setone(bignum25519 out) {
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// (cathugger) this hopefuly will get inlined by compiler because im lazy
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curve25519_expand(out, curve25519_packedone);
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}
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/*
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* (cathugger)
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* idk if recip is same as invert but I hope it is
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* if that's the case then we're doing batch invert there
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*/
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static void
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curve25519_batchrecip(bignum25519 *out, const bignum25519 *in, bignum25519 *tmp, size_t num, size_t offset) {
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bignum25519 ALIGN(16) acc,tmpacc;
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size_t i;
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const bignum25519 *inp;
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bignum25519 *outp;
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curve25519_setone(acc);
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inp = in;
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for (i = 0; i < num; ++i) {
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curve25519_copy(tmp[i], acc);
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curve25519_mul(acc, acc, *inp);
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inp = (const bignum25519 *)((const char *)inp + offset);
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}
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curve25519_recip(acc, acc);
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i = num;
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inp = (const bignum25519 *)((const char *)in + offset * num);
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outp = (bignum25519 *)((char *)out + offset * num);
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while (i--) {
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inp = (const bignum25519 *)((const char *)inp - offset);
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outp = (bignum25519 *)((char *)outp - offset);
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curve25519_mul(tmpacc, acc, *inp);
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curve25519_mul(*outp, acc, tmp[i]);
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curve25519_copy(acc, tmpacc);
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}
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}
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/*
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* z^((p-5)/8) = z^(2^252 - 3)
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*/
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static void
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curve25519_pow_two252m3(bignum25519 two252m3, const bignum25519 z) {
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bignum25519 ALIGN(16) b,c,t0;
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/* 2 */ curve25519_square_times(c, z, 1); /* c = 2 */
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/* 8 */ curve25519_square_times(t0, c, 2); /* t0 = 8 */
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/* 9 */ curve25519_mul_noinline(b, t0, z); /* b = 9 */
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/* 11 */ curve25519_mul_noinline(c, b, c); /* c = 11 */
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/* 22 */ curve25519_square_times(t0, c, 1);
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/* 2^5 - 2^0 = 31 */ curve25519_mul_noinline(b, t0, b);
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/* 2^250 - 2^0 */ curve25519_pow_two5mtwo0_two250mtwo0(b);
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/* 2^252 - 2^2 */ curve25519_square_times(b, b, 2);
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/* 2^252 - 3 */ curve25519_mul_noinline(two252m3, b, z);
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}
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