catcrypt: Implement symmetric key-encapsulation and signature schemes.

[u/mdw/catacomb] / gf-arith.c

diff --git a/gf-arith.c b/gf-arith.c
index f380a35..eabbff8 100644 (file)
--- a/gf-arith.c
+++ b/gf-arith.c
@@ -179,11 +179,17 @@ void gf_div(mp **qq, mp **rr, mp *a, mp *b)
 
 int gf_irreduciblep(mp *f)
 {
-  unsigned long m = mp_bits(f) - 1;
+  unsigned long m;
   mp *u = MP_TWO;
   mp *v = MP_NEW;
 
-  m /= 2;
+  if (MP_ZEROP(f))
+    return (0);
+  else if (MP_LEN(f) == 1) {
+    if (f->v[0] < 2) return (0);
+    if (f->v[0] < 4) return (1);
+  }
+  m = (mp_bits(f) - 1)/2;
   while (m) {
     u = gf_sqr(u, u);
     gf_div(0, &u, u, f);