--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libtommath/bn_mp_expt_u32.c	Thu Oct 15 19:55:15 2020 +0800
@@ -0,0 +1,46 @@
+#include "tommath_private.h"
+#ifdef BN_MP_EXPT_U32_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+/* calculate c = a**b  using a square-multiply algorithm */
+mp_err mp_expt_u32(const mp_int *a, uint32_t b, mp_int *c)
+{
+   mp_err err;
+
+   mp_int  g;
+
+   if ((err = mp_init_copy(&g, a)) != MP_OKAY) {
+      return err;
+   }
+
+   /* set initial result */
+   mp_set(c, 1uL);
+
+   while (b > 0u) {
+      /* if the bit is set multiply */
+      if ((b & 1u) != 0u) {
+         if ((err = mp_mul(c, &g, c)) != MP_OKAY) {
+            goto LBL_ERR;
+         }
+      }
+
+      /* square */
+      if (b > 1u) {
+         if ((err = mp_sqr(&g, &g)) != MP_OKAY) {
+            goto LBL_ERR;
+         }
+      }
+
+      /* shift to next bit */
+      b >>= 1;
+   }
+
+   err = MP_OKAY;
+
+LBL_ERR:
+   mp_clear(&g);
+   return err;
+}
+
+#endif