X-Git-Url: https://git.distorted.org.uk/~mdw/catacomb/blobdiff_plain/373641eaacc86b56715a2ebf0b603fce25c16051..bd4902364e73cb062407b972ef7fecef3998d46a:/math/strongprime.c

diff --git a/math/strongprime.c b/math/strongprime.c
index 9eab8b20..5b136534 100644
--- a/math/strongprime.c
+++ b/math/strongprime.c
@@ -140,17 +140,10 @@ mp *strongprime_setup(const char *name, mp *d, pfilt *f, unsigned nbits,
    * This computes %$p_0 = 2 s (s^{r - 2} \bmod r) - 1$%.
    */
 
-  {
-    mpmont mm;
-
-    mpmont_create(&mm, q);
-    rr = mp_sub(rr, q, MP_TWO);
-    rr = mpmont_exp(&mm, rr, s, rr);
-    mpmont_destroy(&mm);
-    rr = mp_mul(rr, rr, s);
-    rr = mp_lsl(rr, rr, 1);
-    rr = mp_sub(rr, rr, MP_ONE);
-  }
+  rr = mp_modinv(rr, s, q);
+  rr = mp_mul(rr, rr, s);
+  rr = mp_lsl(rr, rr, 1);
+  rr = mp_sub(rr, rr, MP_ONE);
 
   /* --- Pick a starting point for the search --- *
    *