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Merge pull request #739 from JacobBarthelmeh/Memory

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reduction of mp_jacobi stack usage
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toddouska 2017-02-06 11:59:52 -08:00 committed by GitHub
commit 1f7976a587
1 changed files with 42 additions and 26 deletions
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68
wolfcrypt/src/ecc.c
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@ -7004,14 +7004,10 @@ int wc_ecc_decrypt(ecc_key* privKey, ecc_key* pubKey, const byte* msg,
#ifdef HAVE_COMP_KEY
#ifndef WOLFSSL_ATECC508A
/* computes the jacobi c = (a | n) (or Legendre if n is prime)
* HAC pp. 73 Algorithm 2.149
* HAC is wrong here, as the special case of (0 | 1) is not
* handled correctly.
*/
int mp_jacobi(mp_int* a, mp_int* n, int* c)
int do_mp_jacobi(mp_int* a, mp_int* n, int* c);
int do_mp_jacobi(mp_int* a, mp_int* n, int* c)
{
mp_int a1, p1;
int k, s, r, res;
mp_digit residue;
@ -7045,18 +7041,9 @@ int mp_jacobi(mp_int* a, mp_int* n, int* c)
/* default */
s = 0;
/* step 3. write a = a1 * 2**k */
if ((res = mp_init_multi(&a1, &p1, NULL, NULL, NULL, NULL)) != MP_OKAY) {
return res;
}
if ((res = mp_copy(a, &a1)) != MP_OKAY) {
goto done;
}
/* divide out larger power of two */
k = mp_cnt_lsb(&a1);
res = mp_div_2d(&a1, k, &a1, NULL);
k = mp_cnt_lsb(a);
res = mp_div_2d(a, k, a, NULL);
if (res == MP_OKAY) {
/* step 4. if e is even set s=1 */
@ -7073,31 +7060,60 @@ int mp_jacobi(mp_int* a, mp_int* n, int* c)
}
}
/* step 5. if p == 3 (mod 4) *and* a1 == 3 (mod 4) then s = -s */
if ( ((n->dp[0] & 3) == 3) && ((a1.dp[0] & 3) == 3)) {
/* step 5. if p == 3 (mod 4) *and* a == 3 (mod 4) then s = -s */
if ( ((n->dp[0] & 3) == 3) && ((a->dp[0] & 3) == 3)) {
s = -s;
}
}
if (res == MP_OKAY) {
/* if a1 == 1 we're done */
if (mp_cmp_d (&a1, 1) == MP_EQ) {
/* if a == 1 we're done */
if (mp_cmp_d(a, 1) == MP_EQ) {
*c = s;
} else {
/* n1 = n mod a1 */
res = mp_mod (n, &a1, &p1);
/* n1 = n mod a */
res = mp_mod (n, a, n);
if (res == MP_OKAY)
res = mp_jacobi (&p1, &a1, &r);
res = do_mp_jacobi(n, a, &r);
if (res == MP_OKAY)
*c = s * r;
}
}
return res;
}
/* computes the jacobi c = (a | n) (or Legendre if n is prime)
* HAC pp. 73 Algorithm 2.149
* HAC is wrong here, as the special case of (0 | 1) is not
* handled correctly.
*/
int mp_jacobi(mp_int* a, mp_int* n, int* c)
{
mp_int a1, n1;
int res;
/* step 3. write a = a1 * 2**k */
if ((res = mp_init_multi(&a1, &n1, NULL, NULL, NULL, NULL)) != MP_OKAY) {
return res;
}
if ((res = mp_copy(a, &a1)) != MP_OKAY) {
goto done;
}
if ((res = mp_copy(n, &n1)) != MP_OKAY) {
goto done;
}
res = do_mp_jacobi(&a1, &n1, c);
done:
/* cleanup */
#ifndef USE_FAST_MATH
mp_clear(&p1);
mp_clear(&n1);
mp_clear(&a1);
#endif