--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pk/dsa/dsa_sign_hash.c	Fri May 06 13:23:02 2005 +0000
@@ -0,0 +1,126 @@
+/* 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, [email protected], http://libtomcrypt.org
+ */
+#include "tomcrypt.h"
+
+/**
+   @file dsa_sign_hash.c
+   DSA implementation, sign a hash, Tom St Denis
+*/
+
+#ifdef MDSA
+
+/**
+  Sign a hash with DSA
+  @param in       The hash to sign
+  @param inlen    The length of the hash to sign
+  @param out      [out] Where to store the signature
+  @param outlen   [in/out] The max size and resulting size of the signature
+  @param prng     An active PRNG state
+  @param wprng    The index of the PRNG desired
+  @param key      A private DSA key
+  @return CRYPT_OK if successful
+*/
+int dsa_sign_hash(const unsigned char *in,  unsigned long inlen,
+                        unsigned char *out, unsigned long *outlen,
+                        prng_state *prng, int wprng, dsa_key *key)
+{
+   mp_int         k, kinv, tmp, r, s;
+   unsigned char *buf;
+   int            err;
+   unsigned long  out1, out2;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_ARGCHK(key    != NULL);
+
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+   if (key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+
+   /* check group order size  */
+   if (key->qord >= MDSA_MAX_GROUP) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   buf = XMALLOC(MDSA_MAX_GROUP);
+   if (buf == NULL) {
+      return CRYPT_MEM;
+   }
+
+   /* Init our temps */
+   if ((err = mp_init_multi(&k, &kinv, &r, &s, &tmp, NULL)) != MP_OKAY)               { goto error; }
+
+retry:
+
+   do {
+      /* gen random k */
+      if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) {
+         err = CRYPT_ERROR_READPRNG;
+         goto LBL_ERR;
+      }
+
+      /* read k */
+      if ((err = mp_read_unsigned_bin(&k, buf, key->qord)) != MP_OKAY)                { goto error; }
+
+      /* k > 1 ? */
+      if (mp_cmp_d(&k, 1) != MP_GT)                                                   { goto retry; }
+
+      /* test gcd */
+      if ((err = mp_gcd(&k, &key->q, &tmp)) != MP_OKAY)                               { goto error; }
+   } while (mp_cmp_d(&tmp, 1) != MP_EQ);
+
+   /* now find 1/k mod q */
+   if ((err = mp_invmod(&k, &key->q, &kinv)) != MP_OKAY)                              { goto error; }
+
+   /* now find r = g^k mod p mod q */
+   if ((err = mp_exptmod(&key->g, &k, &key->p, &r)) != MP_OKAY)                       { goto error; }
+   if ((err = mp_mod(&r, &key->q, &r)) != MP_OKAY)                                    { goto error; }
+
+   if (mp_iszero(&r) == MP_YES)                                                       { goto retry; }
+
+   /* now find s = (in + xr)/k mod q */
+   if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, inlen)) != MP_OKAY)     { goto error; }
+   if ((err = mp_mul(&key->x, &r, &s)) != MP_OKAY)                                    { goto error; }
+   if ((err = mp_add(&s, &tmp, &s)) != MP_OKAY)                                       { goto error; }
+   if ((err = mp_mulmod(&s, &kinv, &key->q, &s)) != MP_OKAY)                          { goto error; }
+
+   if (mp_iszero(&s) == MP_YES)                                                       { goto retry; }
+
+   /* now store em both */
+   
+   /* first check that we have enough room */
+   if ((err = der_length_integer(&s, &out1)) != CRYPT_OK)                             { goto LBL_ERR; }
+   if ((err = der_length_integer(&r, &out2)) != CRYPT_OK)                             { goto LBL_ERR; }
+   if (*outlen < (out1+out2)) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto LBL_ERR;
+   }
+
+   /* store ints */
+   err = der_put_multi_integer(out, outlen, &r, &s, NULL);
+   goto LBL_ERR;
+
+error: 
+   err = mpi_to_ltc_error(err);
+LBL_ERR: 
+   mp_clear_multi(&k, &kinv, &r, &s, &tmp, NULL);
+#ifdef LTC_CLEAN_STACK
+   zeromem(buf, MDSA_MAX_GROUP);
+#endif
+   XFREE(buf);
+   return err;
+}
+
+#endif