1 files changed, 95 insertions, 0 deletions
diff --git a/src/pk/ecc/ecc_shared_secret.c b/src/pk/ecc/ecc_shared_secret.c
new file mode 100644
index 0000000..ddef847
--- /dev/null
+++ b/src/pk/ecc/ecc_shared_secret.c
@@ -0,0 +1,95 @@
+/* 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
+ */
+
+/* Implements ECC over Z/pZ for curve y^2 = x^3 - 3x + b
+ *
+ * All curves taken from NIST recommendation paper of July 1999
+ * Available at http://csrc.nist.gov/cryptval/dss.htm
+ */
+#include "tomcrypt.h"
+
+/**
+  @file ecc_shared_secret.c
+  ECC Crypto, Tom St Denis
+*/  
+
+#ifdef MECC
+
+/**
+  Create an ECC shared secret between two keys
+  @param private_key      The private ECC key
+  @param public_key       The public key
+  @param out              [out] Destination of the shared secret (Conforms to EC-DH from ANSI X9.63)
+  @param outlen           [in/out] The max size and resulting size of the shared secret
+  @return CRYPT_OK if successful
+*/
+int ecc_shared_secret(ecc_key *private_key, ecc_key *public_key,
+                      unsigned char *out, unsigned long *outlen)
+{
+   unsigned long  x;
+   ecc_point     *result;
+   void          *prime;
+   int            err;
+
+   LTC_ARGCHK(private_key != NULL);
+   LTC_ARGCHK(public_key  != NULL);
+   LTC_ARGCHK(out         != NULL);
+   LTC_ARGCHK(outlen      != NULL);
+
+   /* type valid? */
+   if (private_key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   if (ltc_ecc_is_valid_idx(private_key->idx) == 0 || ltc_ecc_is_valid_idx(public_key->idx) == 0) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   if (XSTRCMP(private_key->dp->name, public_key->dp->name) != 0) {
+      return CRYPT_PK_TYPE_MISMATCH;
+   }
+
+   /* make new point */
+   result = ltc_ecc_new_point();
+   if (result == NULL) {
+      return CRYPT_MEM;
+   }
+
+   if ((err = mp_init(&prime)) != CRYPT_OK) {
+      ltc_ecc_del_point(result);
+      return err;
+   }
+
+   if ((err = mp_read_radix(prime, (char *)private_key->dp->prime, 16)) != CRYPT_OK)                               { goto done; }
+   if ((err = ltc_mp.ecc_ptmul(private_key->k, &public_key->pubkey, result, prime, 1)) != CRYPT_OK)                { goto done; }
+
+   x = (unsigned long)mp_unsigned_bin_size(prime);
+   if (*outlen < x) {
+      *outlen = x;
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto done;
+   }
+   zeromem(out, x);
+   if ((err = mp_to_unsigned_bin(result->x, out + (x - mp_unsigned_bin_size(result->x))))   != CRYPT_OK)           { goto done; }
+
+   err     = CRYPT_OK;
+   *outlen = x;
+done:
+   mp_clear(prime);
+   ltc_ecc_del_point(result);
+   return err;
+}
+
+#endif
+/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_shared_secret.c,v $ */
+/* $Revision: 1.8 $ */
+/* $Date: 2006/12/04 02:19:48 $ */
+