diff options
Diffstat (limited to 'libtommath/bn_mp_montgomery_setup.c')
| -rw-r--r-- | libtommath/bn_mp_montgomery_setup.c | 45 |
1 files changed, 22 insertions, 23 deletions
diff --git a/libtommath/bn_mp_montgomery_setup.c b/libtommath/bn_mp_montgomery_setup.c index 1c17445..46f560d 100644 --- a/libtommath/bn_mp_montgomery_setup.c +++ b/libtommath/bn_mp_montgomery_setup.c @@ -16,41 +16,40 @@ */ /* setups the montgomery reduction stuff */ -int -mp_montgomery_setup (mp_int * n, mp_digit * rho) +int mp_montgomery_setup(mp_int *n, mp_digit *rho) { - mp_digit x, b; + mp_digit x, b; -/* fast inversion mod 2**k - * - * Based on the fact that - * - * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) - * => 2*X*A - X*X*A*A = 1 - * => 2*(1) - (1) = 1 - */ - b = n->dp[0]; + /* fast inversion mod 2**k + * + * Based on the fact that + * + * XA = 1 (mod 2**n) => (X(2-XA)) A = 1 (mod 2**2n) + * => 2*X*A - X*X*A*A = 1 + * => 2*(1) - (1) = 1 + */ + b = n->dp[0]; - if ((b & 1) == 0) { - return MP_VAL; - } + if ((b & 1) == 0) { + return MP_VAL; + } - x = (((b + 2) & 4) << 1) + b; /* here x*a==1 mod 2**4 */ - x *= 2 - (b * x); /* here x*a==1 mod 2**8 */ + x = (((b + 2) & 4) << 1) + b; /* here x*a==1 mod 2**4 */ + x *= 2 - (b * x); /* here x*a==1 mod 2**8 */ #if !defined(MP_8BIT) - x *= 2 - (b * x); /* here x*a==1 mod 2**16 */ + x *= 2 - (b * x); /* here x*a==1 mod 2**16 */ #endif #if defined(MP_64BIT) || !(defined(MP_8BIT) || defined(MP_16BIT)) - x *= 2 - (b * x); /* here x*a==1 mod 2**32 */ + x *= 2 - (b * x); /* here x*a==1 mod 2**32 */ #endif #ifdef MP_64BIT - x *= 2 - (b * x); /* here x*a==1 mod 2**64 */ + x *= 2 - (b * x); /* here x*a==1 mod 2**64 */ #endif - /* rho = -1/m mod b */ - *rho = (mp_digit)(((mp_word)1 << ((mp_word) DIGIT_BIT)) - x) & MP_MASK; + /* rho = -1/m mod b */ + *rho = (mp_digit)(((mp_word)1 << ((mp_word) DIGIT_BIT)) - x) & MP_MASK; - return MP_OKAY; + return MP_OKAY; } #endif |