Mercurial > dropbear
diff bn_fast_mp_invmod.c @ 190:d8254fc979e9 libtommath-orig LTM_0.35
Initial import of libtommath 0.35
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Fri, 06 May 2005 08:59:30 +0000 |
parents | d29b64170cf0 |
children |
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--- a/bn_fast_mp_invmod.c Sun Dec 19 11:33:56 2004 +0000 +++ b/bn_fast_mp_invmod.c Fri May 06 08:59:30 2005 +0000 @@ -21,8 +21,7 @@ * Based on slow invmod except this is optimized for the case where b is * odd as per HAC Note 14.64 on pp. 610 */ -int -fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c) +int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c) { mp_int x, y, u, v, B, D; int res, neg; @@ -39,20 +38,20 @@ /* x == modulus, y == value to invert */ if ((res = mp_copy (b, &x)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } /* we need y = |a| */ - if ((res = mp_abs (a, &y)) != MP_OKAY) { - goto __ERR; + if ((res = mp_mod (a, b, &y)) != MP_OKAY) { + goto LBL_ERR; } /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ if ((res = mp_copy (&x, &u)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } if ((res = mp_copy (&y, &v)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } mp_set (&D, 1); @@ -61,17 +60,17 @@ while (mp_iseven (&u) == 1) { /* 4.1 u = u/2 */ if ((res = mp_div_2 (&u, &u)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } /* 4.2 if B is odd then */ if (mp_isodd (&B) == 1) { if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } /* B = B/2 */ if ((res = mp_div_2 (&B, &B)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } @@ -79,18 +78,18 @@ while (mp_iseven (&v) == 1) { /* 5.1 v = v/2 */ if ((res = mp_div_2 (&v, &v)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } /* 5.2 if D is odd then */ if (mp_isodd (&D) == 1) { /* D = (D-x)/2 */ if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } /* D = D/2 */ if ((res = mp_div_2 (&D, &D)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } @@ -98,20 +97,20 @@ if (mp_cmp (&u, &v) != MP_LT) { /* u = u - v, B = B - D */ if ((res = mp_sub (&u, &v, &u)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } if ((res = mp_sub (&B, &D, &B)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } else { /* v - v - u, D = D - B */ if ((res = mp_sub (&v, &u, &v)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } if ((res = mp_sub (&D, &B, &D)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } @@ -125,21 +124,21 @@ /* if v != 1 then there is no inverse */ if (mp_cmp_d (&v, 1) != MP_EQ) { res = MP_VAL; - goto __ERR; + goto LBL_ERR; } /* b is now the inverse */ neg = a->sign; while (D.sign == MP_NEG) { if ((res = mp_add (&D, b, &D)) != MP_OKAY) { - goto __ERR; + goto LBL_ERR; } } mp_exch (&D, c); c->sign = neg; res = MP_OKAY; -__ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL); +LBL_ERR:mp_clear_multi (&x, &y, &u, &v, &B, &D, NULL); return res; } #endif