Commit ba786e6b3936e484d47a99691c730681a514cc06
2018-05-11T00:50:52
Call mp_kronecker from mp_jacobi to save some bytes while keeping the API
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diff --git a/bn_mp_jacobi.c b/bn_mp_jacobi.c
index fe37f22..65fb2d2 100644
--- a/bn_mp_jacobi.c
+++ b/bn_mp_jacobi.c
@@ -14,16 +14,10 @@
*/
/* 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.
+ * Kept for legacy reasons, please use mp_kronecker() instead
*/
int mp_jacobi(const mp_int *a, const mp_int *n, int *c)
{
- mp_int a1, p1;
- int k, s, r, res;
- mp_digit residue;
-
/* if a < 0 return MP_VAL */
if (mp_isneg(a) == MP_YES) {
return MP_VAL;
@@ -34,81 +28,7 @@ int mp_jacobi(const mp_int *a, const mp_int *n, int *c)
return MP_VAL;
}
- /* step 1. handle case of a == 0 */
- if (mp_iszero(a) == MP_YES) {
- /* special case of a == 0 and n == 1 */
- if (mp_cmp_d(n, 1uL) == MP_EQ) {
- *c = 1;
- } else {
- *c = 0;
- }
- return MP_OKAY;
- }
-
- /* step 2. if a == 1, return 1 */
- if (mp_cmp_d(a, 1uL) == MP_EQ) {
- *c = 1;
- return MP_OKAY;
- }
-
- /* default */
- s = 0;
-
- /* step 3. write a = a1 * 2**k */
- if ((res = mp_init_copy(&a1, a)) != MP_OKAY) {
- return res;
- }
-
- if ((res = mp_init(&p1)) != MP_OKAY) {
- goto LBL_A1;
- }
-
- /* divide out larger power of two */
- k = mp_cnt_lsb(&a1);
- if ((res = mp_div_2d(&a1, k, &a1, NULL)) != MP_OKAY) {
- goto LBL_P1;
- }
-
- /* step 4. if e is even set s=1 */
- if (((unsigned)k & 1u) == 0u) {
- s = 1;
- } else {
- /* else set s=1 if p = 1/7 (mod 8) or s=-1 if p = 3/5 (mod 8) */
- residue = n->dp[0] & 7u;
-
- if ((residue == 1u) || (residue == 7u)) {
- s = 1;
- } else if ((residue == 3u) || (residue == 5u)) {
- s = -1;
- }
- }
-
- /* step 5. if p == 3 (mod 4) *and* a1 == 3 (mod 4) then s = -s */
- if (((n->dp[0] & 3u) == 3u) && ((a1.dp[0] & 3u) == 3u)) {
- s = -s;
- }
-
- /* if a1 == 1 we're done */
- if (mp_cmp_d(&a1, 1uL) == MP_EQ) {
- *c = s;
- } else {
- /* n1 = n mod a1 */
- if ((res = mp_mod(n, &a1, &p1)) != MP_OKAY) {
- goto LBL_P1;
- }
- if ((res = mp_jacobi(&p1, &a1, &r)) != MP_OKAY) {
- goto LBL_P1;
- }
- *c = s * r;
- }
-
- /* done */
- res = MP_OKAY;
-LBL_P1:
- mp_clear(&p1);
-LBL_A1:
- mp_clear(&a1);
- return res;
+ return mp_kronecker(a,n,c);
}
#endif