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67 lines
2.4 KiB
C
67 lines
2.4 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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#include "ed25519-donna.h"
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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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void curve25519_pow_two5mtwo0_two250mtwo0(bignum25519 b) {
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bignum25519 ALIGN(16) t0 = {0}, c = {0};
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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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void curve25519_recip(bignum25519 out, const bignum25519 z) {
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bignum25519 ALIGN(16) a = {0}, t0 = {0}, b = {0};
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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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/*
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* z^((p-5)/8) = z^(2^252 - 3)
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*/
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void 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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