minor fixes.

ChangeLog

@@ -1,3 +1,11 @@
+2014-04-14  Niibe Yutaka  <gniibe@fsij.org>
+
+	* src/jpc.c (jpc_to_ac): Error check before mod_inv.
+
+	* src/mod.c (mod_inv): No return value (if N==0 returns ZERO).
+
+	* src/bn.c [BN256_NO_RANDOM]: Only include "random.h" if needed.
+
 2014-04-08  Niibe Yutaka  <gniibe@fsij.org>
 
 	* src/mod.c (mod_inv): Use MAX_GCD_STEPS_BN256.

src/bn.c

@@ -23,7 +23,9 @@
 
 #include <stdint.h>
 #include <string.h>
+#ifndef BN256_NO_RANDOM
 #include "random.h"
+#endif
 #include "bn.h"
 
 uint32_t

src/jpc.c

@@ -185,9 +185,11 @@ FUNC(jpc_to_ac) (ac *X, const jpc *A)
 {
   bn256 z_inv[1], z_inv_sqr[1];
 
-  if (mod_inv (z_inv, A->z, CONST_P256) < 0)
+  if (bn256_is_zero (A->z))
     return -1;
 
+  mod_inv (z_inv, A->z, CONST_P256);
+
   MFNC(sqr) (z_inv_sqr, z_inv);
   MFNC(mul) (z_inv, z_inv, z_inv_sqr);
 

src/mod.c

@@ -147,8 +147,10 @@ mod_reduce (bn256 *X, const bn512 *A, const bn256 *B, const bn256 *MU_lower)
  * @brief C = X^(-1) mod N
  * 
  * Assume X and N are co-prime (or N is prime).
+ * If N==0, return 0.
+ *
  */
-int
+void
 mod_inv (bn256 *C, const bn256 *X, const bn256 *N)
 {
   bn256 u[1], v[1], tmp[1];
@@ -157,9 +159,6 @@ mod_inv (bn256 *C, const bn256 *X, const bn256 *N)
 #define borrow carry
   int n = MAX_GCD_STEPS_BN256;
 
-  if (bn256_is_zero (X))
-    return -1;
-
   memset (C, 0, sizeof (bn256));
   memcpy (u, X, sizeof (bn256));
   memcpy (v, N, sizeof (bn256));
@@ -352,6 +351,4 @@ mod_inv (bn256 *C, const bn256 *X, const bn256 *N)
 	}
     }
 #undef borrow
-
-  return 0;
 }

src/mod.h

@@ -1,3 +1,3 @@
 void mod_reduce (bn256 *X, const bn512 *A, const bn256 *B,
 		 const bn256 *MU_lower);
-int mod_inv (bn256 *X, const bn256 *A, const bn256 *N);
+void mod_inv (bn256 *X, const bn256 *A, const bn256 *N);