1 files changed, 47 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_prime_fermat.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_prime_fermat.c
new file mode 100644
index 0000000..af3e884
--- /dev/null
+++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_prime_fermat.c
@@ -0,0 +1,47 @@
+#include "tommath_private.h"
+#ifdef BN_MP_PRIME_FERMAT_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* performs one Fermat test.
+ *
+ * If "a" were prime then b**a == b (mod a) since the order of
+ * the multiplicative sub-group would be phi(a) = a-1.  That means
+ * it would be the same as b**(a mod (a-1)) == b**1 == b (mod a).
+ *
+ * Sets result to 1 if the congruence holds, or zero otherwise.
+ */
+mp_err mp_prime_fermat(const mp_int *a, const mp_int *b, mp_bool *result)
+{
+   mp_int  t;
+   mp_err  err;
+
+   /* default to composite  */
+   *result = MP_NO;
+
+   /* ensure b > 1 */
+   if (mp_cmp_d(b, 1uL) != MP_GT) {
+      return MP_VAL;
+   }
+
+   /* init t */
+   if ((err = mp_init(&t)) != MP_OKAY) {
+      return err;
+   }
+
+   /* compute t = b**a mod a */
+   if ((err = mp_exptmod(b, a, a, &t)) != MP_OKAY) {
+      goto LBL_T;
+   }
+
+   /* is it equal to b? */
+   if (mp_cmp(&t, b) == MP_EQ) {
+      *result = MP_YES;
+   }
+
+   err = MP_OKAY;
+LBL_T:
+   mp_clear(&t);
+   return err;
+}
+#endif