Commit 857b112ef27efe39735fe1201a86dc8e4afa98e2
2019-09-03T01:04:00
Merge pull request #334 from czurnieden/re_issue_332 repair of #333
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diff --git a/bn_mp_prime_next_prime.c b/bn_mp_prime_next_prime.c
index aaa821b..17abbf8 100644
--- a/bn_mp_prime_next_prime.c
+++ b/bn_mp_prime_next_prime.c
@@ -24,20 +24,17 @@ mp_err mp_prime_next_prime(mp_int *a, int t, int bbs_style)
/* find which prime it is bigger than */
for (x = PRIVATE_MP_PRIME_TAB_SIZE - 2; x >= 0; x--) {
if (mp_cmp_d(a, s_mp_prime_tab[x]) != MP_LT) {
+ /* ok we found a prime smaller or
+ * equal [so the next is larger]
+ */
if (bbs_style == 1) {
- /* ok we found a prime smaller or
- * equal [so the next is larger]
- *
- * however, the prime must be
+ /* ... however, the prime must be
* congruent to 3 mod 4
- */
- if ((s_mp_prime_tab[x + 1] & 3u) != 3u) {
- /* scan upwards for a prime congruent to 3 mod 4 */
- for (y = x + 1; y < PRIVATE_MP_PRIME_TAB_SIZE; y++) {
- if ((s_mp_prime_tab[y] & 3u) == 3u) {
- mp_set(a, s_mp_prime_tab[y]);
- return MP_OKAY;
- }
+ * so do a scan upwards for such a prime */
+ for (y = x + 1; y < PRIVATE_MP_PRIME_TAB_SIZE; y++) {
+ if ((s_mp_prime_tab[y] & 3u) == 3u) {
+ mp_set(a, s_mp_prime_tab[y]);
+ return MP_OKAY;
}
}
} else {
@@ -46,9 +43,13 @@ mp_err mp_prime_next_prime(mp_int *a, int t, int bbs_style)
}
}
}
- /* at this point a maybe 1 */
- if (mp_cmp_d(a, 1uL) == MP_EQ) {
- mp_set(a, 2uL);
+ /* at this point a maybe smaller than the smallest prime in the table */
+ if (mp_cmp_d(a, 2uL) != MP_GT) {
+ if (bbs_style == 1) {
+ mp_set(a, 3uL);
+ } else {
+ mp_set(a, 2uL);
+ }
return MP_OKAY;
}
/* fall through to the sieve */
diff --git a/demo/test.c b/demo/test.c
index 38a75a9..390d32d 100644
--- a/demo/test.c
+++ b/demo/test.c
@@ -1052,6 +1052,136 @@ LBL_ERR:
}
+
+static int test_mp_prime_next_prime(void)
+{
+ mp_err err;
+ mp_int a, b, c;
+
+ mp_init_multi(&a, &b, &c, NULL);
+
+
+ /* edge cases */
+ mp_set(&a, 0u);
+ if ((err = mp_prime_next_prime(&a, 5, 0)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp_d(&a, 2u) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been 2 but was: ");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+
+ mp_set(&a, 0u);
+ if ((err = mp_prime_next_prime(&a, 5, 1)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp_d(&a, 3u) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been 3 but was: ");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+
+ mp_set(&a, 2u);
+ if ((err = mp_prime_next_prime(&a, 5, 0)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp_d(&a, 3u) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been 3 but was: ");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+
+ mp_set(&a, 2u);
+ if ((err = mp_prime_next_prime(&a, 5, 1)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp_d(&a, 3u) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been 3 but was: ");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+ mp_set(&a, 8);
+ if ((err = mp_prime_next_prime(&a, 5, 1)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp_d(&a, 11u) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been 11 but was: ");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+ /* 2^300 + 157 is a 300 bit large prime to guarantee a multi-limb bigint */
+ if ((err = mp_2expt(&a, 300)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ mp_set_u32(&b, 157);
+ if ((err = mp_add(&a, &b, &a)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if ((err = mp_copy(&a, &b)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+
+ /* 2^300 + 385 is the next prime */
+ mp_set_u32(&c, 228);
+ if ((err = mp_add(&b, &c, &b)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if ((err = mp_prime_next_prime(&a, 5, 0)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp(&a, &b) != MP_EQ) {
+ printf("mp_prime_next_prime: output should have been\n");
+ mp_fwrite(&b,10,stdout);
+ putchar('\n');
+ printf("but was:\n");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+
+ /* Use another temporary variable or recompute? Mmh... */
+ if ((err = mp_2expt(&a, 300)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ mp_set_u32(&b, 157);
+ if ((err = mp_add(&a, &b, &a)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if ((err = mp_copy(&a, &b)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+
+ /* 2^300 + 631 is the next prime congruent to 3 mod 4*/
+ mp_set_u32(&c, 474);
+ if ((err = mp_add(&b, &c, &b)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if ((err = mp_prime_next_prime(&a, 5, 1)) != MP_OKAY) {
+ goto LBL_ERR;
+ }
+ if (mp_cmp(&a, &b) != MP_EQ) {
+ printf("mp_prime_next_prime (bbs): output should have been\n");
+ mp_fwrite(&b,10,stdout);
+ putchar('\n');
+ printf("but was:\n");
+ mp_fwrite(&a,10,stdout);
+ putchar('\n');
+ goto LBL_ERR;
+ }
+
+ mp_clear_multi(&a, &b, &c, NULL);
+ return EXIT_SUCCESS;
+LBL_ERR:
+ mp_clear_multi(&a, &b, &c, NULL);
+ return EXIT_FAILURE;
+}
+
static int test_mp_montgomery_reduce(void)
{
mp_digit mp;
@@ -2113,6 +2243,7 @@ int unit_tests(int argc, char **argv)
T(mp_root_u32),
T(mp_or),
T(mp_prime_is_prime),
+ T(mp_prime_next_prime),
T(mp_prime_rand),
T(mp_rand),
T(mp_read_radix),