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

31
wolfcrypt/src/integer.c
View File

@ -1145,23 +1145,28 @@ int mp_invmod_slow (mp_int * a, mp_int * b, mp_int * c)
/* init temps */
if ((res = mp_init_multi(&x, &y, &u, &v,
&A, &B)) != MP_OKAY) {
return res;
return res;
}
/* init rest of tmps temps */
if ((res = mp_init_multi(&C, &D, 0, 0, 0, 0)) != MP_OKAY) {
mp_clear(&x);
mp_clear(&y);
mp_clear(&u);
mp_clear(&v);
mp_clear(&A);
mp_clear(&B);
return res;
mp_clear(&x);
mp_clear(&y);
mp_clear(&u);
mp_clear(&v);
mp_clear(&A);
mp_clear(&B);
return res;
}
/* x = a, y = b */
if ((res = mp_mod(a, b, &x)) != MP_OKAY) {
goto LBL_ERR;
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;
@ -1198,10 +1203,10 @@ top:
if (mp_isodd (&A) == MP_YES || mp_isodd (&B) == MP_YES) {
/* A = (A+y)/2, B = (B-x)/2 */
if ((res = mp_add (&A, &y, &A)) != MP_OKAY) {
goto LBL_ERR;
goto LBL_ERR;
}
if ((res = mp_sub (&B, &x, &B)) != MP_OKAY) {
goto LBL_ERR;
goto LBL_ERR;
}
}
/* A = A/2, B = B/2 */
@ -1223,10 +1228,10 @@ top:
if (mp_isodd (&C) == MP_YES || mp_isodd (&D) == MP_YES) {
/* C = (C+y)/2, D = (D-x)/2 */
if ((res = mp_add (&C, &y, &C)) != MP_OKAY) {
goto LBL_ERR;
goto LBL_ERR;
}
if ((res = mp_sub (&D, &x, &D)) != MP_OKAY) {
goto LBL_ERR;
goto LBL_ERR;
}
}
/* C = C/2, D = D/2 */

30
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);
@ -922,7 +925,7 @@ static int fp_invmod_slow (fp_int * a, fp_int * b, fp_int * c)
fp_copy(b, y);
/* 2. [modified] if x,y are both even then return an error! */
if (fp_iseven (x) == FP_YES && fp_iseven (y) == FP_YES) {
if (fp_iseven(x) == FP_YES && fp_iseven(y) == FP_YES) {
#ifdef WOLFSSL_SMALL_STACK
XFREE(x, NULL, DYNAMIC_TYPE_BIGINT);
#endif
@ -1022,9 +1025,14 @@ 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) {
if (fp_iseven(b) == FP_YES) {
return fp_invmod_slow(a,b,c);
}
@ -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);