diff options
Diffstat (limited to 'src/curve25519-donna-common.h')
| -rw-r--r-- | src/curve25519-donna-common.h | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/src/curve25519-donna-common.h b/src/curve25519-donna-common.h new file mode 100644 index 0000000..741fe1b --- /dev/null +++ b/src/curve25519-donna-common.h @@ -0,0 +1,43 @@ +/* + * In: b = 2^5 - 2^0 + * Out: b = 2^250 - 2^0 + */ +static void +curve25519_pow_two5mtwo0_two250mtwo0(bignum25519 b) { + bignum25519 _ALIGN(16) t0,c; + + /* 2^5 - 2^0 */ /* b */ + /* 2^10 - 2^5 */ curve25519_square_times(t0, b, 5); + /* 2^10 - 2^0 */ curve25519_mul(b, t0, b); + /* 2^20 - 2^10 */ curve25519_square_times(t0, b, 10); + /* 2^20 - 2^0 */ curve25519_mul(c, t0, b); + /* 2^40 - 2^20 */ curve25519_square_times(t0, c, 20); + /* 2^40 - 2^0 */ curve25519_mul(t0, t0, c); + /* 2^50 - 2^10 */ curve25519_square_times(t0, t0, 10); + /* 2^50 - 2^0 */ curve25519_mul(b, t0, b); + /* 2^100 - 2^50 */ curve25519_square_times(t0, b, 50); + /* 2^100 - 2^0 */ curve25519_mul(c, t0, b); + /* 2^200 - 2^100 */ curve25519_square_times(t0, c, 100); + /* 2^200 - 2^0 */ curve25519_mul(t0, t0, c); + /* 2^250 - 2^50 */ curve25519_square_times(t0, t0, 50); + /* 2^250 - 2^0 */ curve25519_mul(b, t0, b); +} + +/* + * z^(p - 2) = z(2^255 - 21) + */ +static void +curve25519_recip(bignum25519 out, const bignum25519 z) { + bignum25519 _ALIGN(16) a,t0,b; + + /* 2 */ curve25519_square(a, z); /* a = 2 */ + /* 8 */ curve25519_square_times(t0, a, 2); + /* 9 */ curve25519_mul(b, t0, z); /* b = 9 */ + /* 11 */ curve25519_mul(a, b, a); /* a = 11 */ + /* 22 */ curve25519_square(t0, a); + /* 2^5 - 2^0 = 31 */ curve25519_mul(b, t0, b); + /* 2^250 - 2^0 */ curve25519_pow_two5mtwo0_two250mtwo0(b); + /* 2^255 - 2^5 */ curve25519_square_times(b, b, 5); + /* 2^255 - 21 */ curve25519_mul(out, b, a); +} + |