--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dsa_sign_hash.c	Mon May 31 18:21:40 2004 +0000
@@ -0,0 +1,125 @@
+/* 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 "mycrypt.h"
+
+#ifdef MDSA
+
+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[512];
+   int err, y;
+   unsigned long len;
+
+
+   _ARGCHK(in     != NULL);
+   _ARGCHK(out    != NULL);
+   _ARGCHK(outlen != NULL);
+   _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 >= (int)sizeof(buf)) {
+      return CRYPT_INVALID_ARG;
+   }
+
+   /* 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 done;
+      }
+
+      /* 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 (*outlen < (unsigned long)(PACKET_SIZE + 4 + mp_unsigned_bin_size(&s) + mp_unsigned_bin_size(&r))) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto done;
+   }
+
+   /* packet header */
+   packet_store_header(out, PACKET_SECT_DSA, PACKET_SUB_SIGNED);
+   y = PACKET_SIZE;
+
+   /* store length of r */
+   len = mp_unsigned_bin_size(&r);
+   out[y++] = (len>>8)&255;
+   out[y++] = len&255;
+   
+   /* store r */
+   if ((err = mp_to_unsigned_bin(&r, out+y)) != MP_OKAY)                              { goto error; }
+   y += len;
+
+   /* store length of s */
+   len = mp_unsigned_bin_size(&s);
+   out[y++] = (len>>8)&255;
+   out[y++] = len&255;
+   
+   /* store s */
+   if ((err = mp_to_unsigned_bin(&s, out+y)) != MP_OKAY)                              { goto error; }
+   y += len;
+
+   /* reset size */
+   *outlen = y;
+
+   err = CRYPT_OK;
+   goto done;
+
+error : err = mpi_to_ltc_error(err);
+done  : mp_clear_multi(&k, &kinv, &r, &s, &tmp, NULL);
+#ifdef CLEAN_STACK
+   zeromem(buf, sizeof(buf));
+#endif
+   return err;
+}
+
+#endif