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Merge branch 'fix/67' into develop

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This closes #67
This commit is contained in:
Steffen Jaeckel 2017-10-15 12:01:15 +02:00
commit efcac86cac
3 changed files with 18 additions and 3 deletions
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6
bn_fast_mp_invmod.c
View File

@ -46,6 +46,12 @@ int fast_mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
goto LBL_ERR; goto LBL_ERR;
} }
/* if one of x,y is zero return an error! */
if ((mp_iszero(&x) == MP_YES) || (mp_iszero(&y) == MP_YES)) {
res = MP_VAL;
goto LBL_ERR;
}
/* 3. u=x, v=y, A=1, B=0, C=0,D=1 */ /* 3. u=x, v=y, A=1, B=0, C=0,D=1 */
if ((res = mp_copy(&x, &u)) != MP_OKAY) { if ((res = mp_copy(&x, &u)) != MP_OKAY) {
goto LBL_ERR; goto LBL_ERR;

6
bn_mp_invmod.c
View File

@ -18,14 +18,14 @@
/* hac 14.61, pp608 */ /* hac 14.61, pp608 */
int mp_invmod(const mp_int *a, const mp_int *b, mp_int *c) int mp_invmod(const mp_int *a, const mp_int *b, mp_int *c)
{ {
/* b cannot be negative */ /* b cannot be negative and has to be >1 */
if ((b->sign == MP_NEG) || (mp_iszero(b) == MP_YES)) { if ((b->sign == MP_NEG) || (mp_cmp_d(b, 1) != MP_GT)) {
return MP_VAL; return MP_VAL;
} }
#ifdef BN_FAST_MP_INVMOD_C #ifdef BN_FAST_MP_INVMOD_C
/* if the modulus is odd we can use a faster routine instead */ /* if the modulus is odd we can use a faster routine instead */
if ((mp_isodd(b) == MP_YES) && (mp_cmp_d(b, 1) != MP_EQ)) { if ((mp_isodd(b) == MP_YES)) {
return fast_mp_invmod(a, b, c); return fast_mp_invmod(a, b, c);
} }
#endif #endif

9
demo/demo.c
View File

@ -229,6 +229,15 @@ int main(void)
return EXIT_FAILURE; return EXIT_FAILURE;
} }
mp_set_int(&a, 42);
mp_set_int(&b, 1);
mp_neg(&b, &b);
mp_set_int(&c, 1);
mp_exptmod(&a, &b, &c, &d);
mp_set_int(&c, 7);
mp_exptmod(&a, &b, &c, &d);
mp_set_int(&a, 0); mp_set_int(&a, 0);
mp_set_int(&b, 1); mp_set_int(&b, 1);