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Fix fastmath and heapmath invmod to be consistent with sp-math.

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This commit is contained in:
jordan
2023-06-02 22:11:44 -05:00
parent 5604033902
commit db28d38ea3
2 changed files with 36 additions and 18 deletions
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17
wolfcrypt/src/integer.c
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@@ -1058,7 +1058,7 @@ int 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, loop_check = 0;
int res, loop_check = 0;
/* 2. [modified] b must be odd */
if (mp_iseven (b) == MP_YES) {
@@ -1080,6 +1080,12 @@ int fast_mp_invmod (mp_int * a, mp_int * b, mp_int * c)
goto LBL_ERR;
}
if (mp_iszero (&y) == MP_YES) {
/* invmod doesn't exist for this a and b */
res = MP_VAL;
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 LBL_ERR;
@@ -1168,7 +1174,6 @@ top:
}
/* b is now the inverse */
neg = a->sign;
while (D.sign == MP_NEG) {
if ((res = mp_add (&D, b, &D)) != MP_OKAY) {
goto LBL_ERR;
@@ -1181,7 +1186,6 @@ top:
}
}
mp_exch (&D, c);
c->sign = neg;
res = MP_OKAY;
LBL_ERR:mp_clear(&x);
@@ -1226,6 +1230,13 @@ 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_iszero (&x) == MP_YES) {
/* invmod doesn't exist for this a and b */
res = MP_VAL;
goto LBL_ERR;
}
if (mp_isone(&x)) {
res = mp_set(c, 1);
goto LBL_ERR;