feedc0de/wolfssl
1
0
Fork 0
forked from wolfSSL/wolfssl
Code Pull Requests Activity

mp_invmod handles more inputs

Browse Source 
Value to invert: a
Modulus: b
integer.c - normal math
  - a is one, or a mod b is one
tfm.c - fast math
  - b is -ve (error), or b is zero
  - a is zero or a mod b is zero
This commit is contained in:
Sean Parkinson
2019-11-29 09:08:44 +10:00
parent b396ed0984
commit bd7a572a8f
2 changed files with 46 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
wolfcrypt/src/integer.c
View File

@ -1163,6 +1163,11 @@ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
if ((res = mp_mod(a, b, &x)) != MP_OKAY) {
goto LBL_ERR;
}
if (mp_isone(&x)) {
mp_set(c, 1);
res = MP_OKAY;
goto LBL_ERR;
}
if ((res = mp_copy (b, &y)) != MP_OKAY) {
goto LBL_ERR;
}

26
wolfcrypt/src/tfm.c
View File

@ -897,6 +897,9 @@ static int fp_invmod_slow (fp_int * a, fp_int * b, fp_int * c)
if (b->sign == FP_NEG || fp_iszero(b) == FP_YES) {
return FP_VAL;
}
if (fp_iszero(a) == FP_YES) {
return FP_VAL;
}
#ifdef WOLFSSL_SMALL_STACK
x = (fp_int*)XMALLOC(sizeof(fp_int) * 8, NULL, DYNAMIC_TYPE_BIGINT);
@ -1022,6 +1025,11 @@ int fp_invmod(fp_int *a, fp_int *b, fp_int *c)
fp_int *x, *y, *u, *v, *B, *D;
#endif
int neg;
int err;
if (b->sign == FP_NEG || fp_iszero(b) == FP_YES) {
return FP_VAL;
}
/* 2. [modified] b must be odd */
if (fp_iseven(b) == FP_YES) {
@ -1041,6 +1049,24 @@ int fp_invmod(fp_int *a, fp_int *b, fp_int *c)
fp_init(u); fp_init(v);
fp_init(B); fp_init(D);
if (fp_cmp(a, b) != MP_LT) {
err = mp_mod(a, b, y);
if (err != FP_OKAY) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(x, NULL, DYNAMIC_TYPE_BIGINT);
#endif
return err;
}
a = y;
}
if (fp_iszero(a) == FP_YES) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(x, NULL, DYNAMIC_TYPE_BIGINT);
#endif
return FP_VAL;
}
/* x == modulus, y == value to invert */
fp_copy(b, x);