mirror of
https://github.com/trezor/trezor-firmware.git
synced 2024-10-16 12:59:06 +00:00
44 lines
1.4 KiB
C
44 lines
1.4 KiB
C
/*
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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(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(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(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(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(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(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(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(a, z); /* a = 2 */
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/* 8 */ curve25519_square_times(t0, a, 2);
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/* 9 */ curve25519_mul(b, t0, z); /* b = 9 */
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/* 11 */ curve25519_mul(a, b, a); /* a = 11 */
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/* 22 */ curve25519_square(t0, a);
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/* 2^5 - 2^0 = 31 */ curve25519_mul(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(out, b, a);
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}
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