diff --git a/wolfcrypt/src/rsa.c b/wolfcrypt/src/rsa.c
index f3119b88e..3ed26f3ef 100644
--- a/wolfcrypt/src/rsa.c
+++ b/wolfcrypt/src/rsa.c
@@ -2256,7 +2256,7 @@ static int wc_RsaFunctionSync(const byte* in, word32 inLen, byte* out,
         #ifdef WOLFSSL_XILINX_CRYPT
             ret = wc_RsaFunctionXil(in, inLen, out, outLen, type, key, rng);
         #else
-            if (mp_exptmod(tmp, &key->e, &key->n, tmp) != MP_OKAY)
+            if (mp_exptmod_nct(tmp, &key->e, &key->n, tmp) != MP_OKAY)
                 ret = MP_EXPTMOD_E;
         #endif
             break;
diff --git a/wolfcrypt/src/tfm.c b/wolfcrypt/src/tfm.c
index be84dee25..059197fc4 100644
--- a/wolfcrypt/src/tfm.c
+++ b/wolfcrypt/src/tfm.c
@@ -1564,7 +1564,8 @@ int fp_exptmod_nb(exptModNb_t* nb, fp_int* G, fp_int* X, fp_int* P, fp_int* Y)
    Based on work by Marc Joye, Sung-Ming Yen, "The Montgomery Powering Ladder",
    Cryptographic Hardware and Embedded Systems, CHES 2002
 */
-static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int * Y)
+static int _fp_exptmod_ct(fp_int * G, fp_int * X, int digits, fp_int * P,
+                          fp_int * Y)
 {
 #ifndef WOLFSSL_SMALL_STACK
 #ifdef WC_NO_CACHE_RESISTANT
@@ -1701,25 +1702,17 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int *
    return err;
 }
 
-#else /* TFM_TIMING_RESISTANT */
+#endif /* TFM_TIMING_RESISTANT */
 
 /* y = g**x (mod b)
  * Some restrictions... x must be positive and < b
  */
-static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
-                       fp_int * Y)
+static int _fp_exptmod_nct(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
 {
-  fp_digit buf, mp;
-  int      err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize;
-#ifdef WOLFSSL_SMALL_STACK
   fp_int  *res;
   fp_int  *M;
-#else
-  fp_int   res[1];
-  fp_int   M[64];
-#endif
-
-  (void)digits;
+  fp_digit buf, mp;
+  int      err, bitbuf, bitcpy, bitcnt, mode, digidx, x, y, winsize;
 
   /* find window size */
   x = fp_count_bits (X);
@@ -1740,14 +1733,13 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
      return err;
   }
 
-#ifdef WOLFSSL_SMALL_STACK
   /* only allocate space for what's needed for window plus res */
-  M = (fp_int*)XMALLOC(sizeof(fp_int)*((1 << winsize) + 1), NULL, DYNAMIC_TYPE_BIGINT);
+  M = (fp_int*)XMALLOC(sizeof(fp_int)*((1 << winsize) + 1), NULL,
+                                                           DYNAMIC_TYPE_BIGINT);
   if (M == NULL) {
      return FP_MEM;
   }
   res = &M[1 << winsize];
-#endif
 
   /* init M array */
   for(x = 0; x < (1 << winsize); x++)
@@ -1782,9 +1774,7 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
     fp_sqr (&M[1 << (winsize - 1)], &M[1 << (winsize - 1)]);
     err = fp_montgomery_reduce (&M[1 << (winsize - 1)], P, mp);
     if (err != FP_OKAY) {
-    #ifdef WOLFSSL_SMALL_STACK
       XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-    #endif
       return err;
     }
   }
@@ -1793,23 +1783,19 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
   for (x = (1 << (winsize - 1)) + 1; x < (1 << winsize); x++) {
     err = fp_mul(&M[x - 1], &M[1], &M[x]);
     if (err != FP_OKAY) {
-    #ifdef WOLFSSL_SMALL_STACK
       XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-    #endif
       return err;
     }
     err = fp_montgomery_reduce(&M[x], P, mp);
     if (err != FP_OKAY) {
-    #ifdef WOLFSSL_SMALL_STACK
       XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-    #endif
       return err;
     }
   }
 
   /* set initial mode and bit cnt */
   mode   = 0;
-  bitcnt = 1;
+  bitcnt = (x % DIGIT_BIT) + 1;
   buf    = 0;
   digidx = X->used - 1;
   bitcpy = 0;
@@ -1844,16 +1830,12 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
     if (mode == 1 && y == 0) {
       err = fp_sqr(res, res);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
       fp_montgomery_reduce(res, P, mp);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
       continue;
@@ -1869,16 +1851,12 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
       for (x = 0; x < winsize; x++) {
         err = fp_sqr(res, res);
         if (err != FP_OKAY) {
-        #ifdef WOLFSSL_SMALL_STACK
           XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-        #endif
           return err;
         }
         err = fp_montgomery_reduce(res, P, mp);
         if (err != FP_OKAY) {
-        #ifdef WOLFSSL_SMALL_STACK
           XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-        #endif
           return err;
         }
       }
@@ -1886,16 +1864,12 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
       /* then multiply */
       err = fp_mul(res, &M[bitbuf], res);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
       err = fp_montgomery_reduce(res, P, mp);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
 
@@ -1912,16 +1886,12 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
     for (x = 0; x < bitcpy; x++) {
       err = fp_sqr(res, res);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
       err = fp_montgomery_reduce(res, P, mp);
       if (err != FP_OKAY) {
-      #ifdef WOLFSSL_SMALL_STACK
         XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-      #endif
         return err;
       }
 
@@ -1931,16 +1901,12 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
         /* then multiply */
         err = fp_mul(res, &M[1], res);
         if (err != FP_OKAY) {
-        #ifdef WOLFSSL_SMALL_STACK
           XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-        #endif
           return err;
         }
         err = fp_montgomery_reduce(res, P, mp);
         if (err != FP_OKAY) {
-        #ifdef WOLFSSL_SMALL_STACK
           XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-        #endif
           return err;
         }
       }
@@ -1958,14 +1924,10 @@ static int _fp_exptmod(fp_int * G, fp_int * X, int digits, fp_int * P,
   /* swap res with Y */
   fp_copy (res, Y);
 
-#ifdef WOLFSSL_SMALL_STACK
   XFREE(M, NULL, DYNAMIC_TYPE_BIGINT);
-#endif
   return err;
 }
 
-#endif /* TFM_TIMING_RESISTANT */
-
 
 #ifdef TFM_TIMING_RESISTANT
 #if DIGIT_BIT <= 16
@@ -2331,7 +2293,11 @@ int fp_exptmod(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
       if (err == FP_OKAY) {
          fp_copy(X, &tmp[1]);
          tmp[1].sign = FP_ZPOS;
-         err =  _fp_exptmod(&tmp[0], &tmp[1], tmp[1].used, P, Y);
+#ifdef TFM_TIMING_RESISTANT
+         err =  _fp_exptmod_ct(&tmp[0], &tmp[1], tmp[1].used, P, Y);
+#else
+         err =  _fp_exptmod_nct(&tmp[0], &tmp[1], P, Y);
+#endif
          if (P->sign == FP_NEG) {
             fp_add(Y, P, Y);
          }
@@ -2349,7 +2315,11 @@ int fp_exptmod(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
    }
    else {
       /* Positive exponent so just exptmod */
-      return _fp_exptmod(G, X, X->used, P, Y);
+#ifdef TFM_TIMING_RESISTANT
+      return _fp_exptmod_ct(G, X, X->used, P, Y);
+#else
+      return _fp_exptmod_nct(G, X, P, Y);
+#endif
    }
 }
 
@@ -2400,7 +2370,12 @@ int fp_exptmod_ex(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int * Y)
       err = fp_invmod(&tmp[0], &tmp[1], &tmp[0]);
       if (err == FP_OKAY) {
          X->sign = FP_ZPOS;
-         err =  _fp_exptmod(&tmp[0], X, digits, P, Y);
+#ifdef TFM_TIMING_RESISTANT
+         err =  _fp_exptmod_ct(&tmp[0], X, digits, P, Y);
+#else
+         err =  _fp_exptmod_nct(&tmp[0], X, P, Y);
+         (void)digits;
+#endif
          if (X != Y) {
             X->sign = FP_NEG;
          }
@@ -2418,10 +2393,81 @@ int fp_exptmod_ex(fp_int * G, fp_int * X, int digits, fp_int * P, fp_int * Y)
    }
    else {
       /* Positive exponent so just exptmod */
-      return _fp_exptmod(G, X, digits, P, Y);
+#ifdef TFM_TIMING_RESISTANT
+      return _fp_exptmod_ct(G, X, digits, P, Y);
+#else
+      return  _fp_exptmod_nct(G, X, P, Y);
+#endif
    }
 }
 
+int fp_exptmod_nct(fp_int * G, fp_int * X, fp_int * P, fp_int * Y)
+{
+#if defined(WOLFSSL_ESP32WROOM32_CRYPT_RSA_PRI) && \
+   !defined(NO_WOLFSSL_ESP32WROOM32_CRYPT_RSA_PRI)
+   int x = fp_count_bits (X);
+#endif
+
+   if (fp_iszero(G)) {
+      fp_set(G, 0);
+      return FP_OKAY;
+   }
+
+   /* prevent overflows */
+   if (P->used > (FP_SIZE/2)) {
+      return FP_VAL;
+   }
+
+#if defined(WOLFSSL_ESP32WROOM32_CRYPT_RSA_PRI) && \
+   !defined(NO_WOLFSSL_ESP32WROOM32_CRYPT_RSA_PRI)
+   if(x > EPS_RSA_EXPT_XBTIS) {
+      return esp_mp_exptmod(G, X, x, P, Y);
+   }
+#endif
+
+   if (X->sign == FP_NEG) {
+#ifndef POSITIVE_EXP_ONLY  /* reduce stack if assume no negatives */
+      int    err;
+   #ifndef WOLFSSL_SMALL_STACK
+      fp_int tmp[2];
+   #else
+      fp_int *tmp;
+   #endif
+
+   #ifdef WOLFSSL_SMALL_STACK
+      tmp = (fp_int*)XMALLOC(sizeof(fp_int) * 2, NULL, DYNAMIC_TYPE_TMP_BUFFER);
+      if (tmp == NULL)
+          return FP_MEM;
+   #endif
+
+      /* yes, copy G and invmod it */
+      fp_init_copy(&tmp[0], G);
+      fp_init_copy(&tmp[1], P);
+      tmp[1].sign = FP_ZPOS;
+      err = fp_invmod(&tmp[0], &tmp[1], &tmp[0]);
+      if (err == FP_OKAY) {
+         X->sign = FP_ZPOS;
+         err =  _fp_exptmod_nct(&tmp[0], X, P, Y);
+         if (X != Y) {
+            X->sign = FP_NEG;
+         }
+         if (P->sign == FP_NEG) {
+            fp_add(Y, P, Y);
+         }
+      }
+   #ifdef WOLFSSL_SMALL_STACK
+      XFREE(tmp, NULL, DYNAMIC_TYPE_BIGINT);
+   #endif
+      return err;
+#else
+      return FP_VAL;
+#endif
+   }
+   else {
+      /* Positive exponent so just exptmod */
+      return  _fp_exptmod_nct(G, X, P, Y);
+   }
+}
 
 /* computes a = 2**b */
 void fp_2expt(fp_int *a, int b)
@@ -3639,6 +3685,12 @@ int mp_exptmod_ex (mp_int * G, mp_int * X, int digits, mp_int * P, mp_int * Y)
   return fp_exptmod_ex(G, X, digits, P, Y);
 }
 
+int mp_exptmod_nct (mp_int * G, mp_int * X, mp_int * P, mp_int * Y)
+{
+  return fp_exptmod_nct(G, X, P, Y);
+}
+
+
 /* compare two ints (signed)*/
 int mp_cmp (mp_int * a, mp_int * b)
 {
diff --git a/wolfssl/wolfcrypt/integer.h b/wolfssl/wolfcrypt/integer.h
index 216f9ae37..03ea908c3 100644
--- a/wolfssl/wolfcrypt/integer.h
+++ b/wolfssl/wolfcrypt/integer.h
@@ -328,6 +328,7 @@ MP_API int  mp_dr_is_modulus(mp_int *a);
 MP_API int  mp_exptmod_fast (mp_int * G, mp_int * X, mp_int * P, mp_int * Y,
                              int);
 MP_API int  mp_exptmod_base_2 (mp_int * X, mp_int * P, mp_int * Y);
+#define mp_exptmod_nct(G,X,P,Y)    mp_exptmod_fast(G,X,P,Y,0)
 MP_API int  mp_montgomery_setup (mp_int * n, mp_digit * rho);
 int  fast_mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho);
 MP_API int  mp_montgomery_reduce (mp_int * x, mp_int * n, mp_digit rho);
diff --git a/wolfssl/wolfcrypt/sp_int.h b/wolfssl/wolfcrypt/sp_int.h
index 344e735e8..df963951c 100644
--- a/wolfssl/wolfcrypt/sp_int.h
+++ b/wolfssl/wolfcrypt/sp_int.h
@@ -272,6 +272,7 @@ MP_API int sp_mul_d(sp_int* a, sp_int_digit n, sp_int* r);
 #define mp_invmod                   sp_invmod
 #define mp_lcm                      sp_lcm
 #define mp_exptmod                  sp_exptmod
+#define mp_exptmod_nct              sp_exptmod
 #define mp_prime_is_prime           sp_prime_is_prime
 #define mp_prime_is_prime_ex        sp_prime_is_prime_ex
 #define mp_exch                     sp_exch
diff --git a/wolfssl/wolfcrypt/tfm.h b/wolfssl/wolfcrypt/tfm.h
index e8b41248e..b11c7f5a3 100644
--- a/wolfssl/wolfcrypt/tfm.h
+++ b/wolfssl/wolfcrypt/tfm.h
@@ -557,6 +557,7 @@ int fp_montgomery_reduce(fp_int *a, fp_int *m, fp_digit mp);
 /* d = a**b (mod c) */
 int fp_exptmod(fp_int *a, fp_int *b, fp_int *c, fp_int *d);
 int fp_exptmod_ex(fp_int *a, fp_int *b, int minDigits, fp_int *c, fp_int *d);
+int fp_exptmod_nct(fp_int *a, fp_int *b, fp_int *c, fp_int *d);
 
 #ifdef WC_RSA_NONBLOCK
 
@@ -748,6 +749,7 @@ MP_API int  mp_invmod_mont_ct(mp_int *a, mp_int *b, mp_int *c, fp_digit mp);
 MP_API int  mp_exptmod (mp_int * g, mp_int * x, mp_int * p, mp_int * y);
 MP_API int  mp_exptmod_ex (mp_int * g, mp_int * x, int minDigits, mp_int * p,
                            mp_int * y);
+MP_API int  mp_exptmod_nct (mp_int * g, mp_int * x, mp_int * p, mp_int * y);
 MP_API int  mp_mul_2d(mp_int *a, int b, mp_int *c);
 MP_API int  mp_2expt(mp_int* a, int b);