1 files changed, 87 insertions, 0 deletions
diff --git a/libtomcrypt/src/math/rand_prime.c b/libtomcrypt/src/math/rand_prime.c
new file mode 100644
index 0000000..05477fe
--- /dev/null
+++ b/libtomcrypt/src/math/rand_prime.c
@@ -0,0 +1,87 @@
+/* LibTomCrypt, modular cryptographic library -- Tom St Denis
+ *
+ * LibTomCrypt is a library that provides various cryptographic
+ * algorithms in a highly modular and flexible manner.
+ *
+ * The library is free for all purposes without any express
+ * guarantee it works.
+ *
+ * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.com
+ */
+#include "tomcrypt.h"
+
+/**
+  @file rand_prime.c
+  Generate a random prime, Tom St Denis
+*/  
+
+#define USE_BBS 1
+
+int rand_prime(void *N, long len, prng_state *prng, int wprng)
+{
+   int            err, res, type;
+   unsigned char *buf;
+
+   LTC_ARGCHK(N != NULL);
+
+   /* get type */
+   if (len < 0) {
+      type = USE_BBS;
+      len = -len;
+   } else {
+      type = 0;
+   }
+
+   /* allow sizes between 2 and 512 bytes for a prime size */
+   if (len < 2 || len > 512) { 
+      return CRYPT_INVALID_PRIME_SIZE;
+   }
+   
+   /* valid PRNG? Better be! */
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err; 
+   }
+
+   /* allocate buffer to work with */
+   buf = XCALLOC(1, len);
+   if (buf == NULL) {
+       return CRYPT_MEM;
+   }
+
+   do {
+      /* generate value */
+      if (prng_descriptor[wprng].read(buf, len, prng) != (unsigned long)len) {
+         XFREE(buf);
+         return CRYPT_ERROR_READPRNG;
+      }
+
+      /* munge bits */
+      buf[0]     |= 0x80 | 0x40;
+      buf[len-1] |= 0x01 | ((type & USE_BBS) ? 0x02 : 0x00);
+ 
+      /* load value */
+      if ((err = mp_read_unsigned_bin(N, buf, len)) != CRYPT_OK) {
+         XFREE(buf);
+         return err;
+      }
+
+      /* test */
+      if ((err = mp_prime_is_prime(N, 8, &res)) != CRYPT_OK) {
+         XFREE(buf);
+         return err;
+      }
+   } while (res == LTC_MP_NO);
+
+#ifdef LTC_CLEAN_STACK
+   zeromem(buf, len);
+#endif
+
+   XFREE(buf);
+   return CRYPT_OK;
+}
+      
+
+
+/* $Source: /cvs/libtom/libtomcrypt/src/math/rand_prime.c,v $ */
+/* $Revision: 1.6 $ */
+/* $Date: 2006/03/31 14:15:35 $ */