--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ecc_sys.c	Mon May 31 18:25:41 2004 +0000
@@ -0,0 +1,432 @@
+/* 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
+ */
+int ecc_encrypt_key(const unsigned char *inkey, unsigned long keylen,
+                          unsigned char *out,  unsigned long *len, 
+                          prng_state *prng, int wprng, int hash, 
+                          ecc_key *key)
+{
+    unsigned char pub_expt[256], ecc_shared[256], skey[MAXBLOCKSIZE];
+    ecc_key pubkey;
+    unsigned long x, y, z, hashsize, pubkeysize;
+    int err;
+
+    _ARGCHK(inkey != NULL);
+    _ARGCHK(out   != NULL);
+    _ARGCHK(len   != NULL);
+    _ARGCHK(key   != NULL);
+
+    /* check that wprng/cipher/hash are not invalid */
+    if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+       return err;
+    }
+
+    if ((err = hash_is_valid(hash)) != CRYPT_OK) {
+       return err;
+    }
+
+    if (keylen > hash_descriptor[hash].hashsize) {
+       return CRYPT_INVALID_HASH;
+    }
+
+    /* make a random key and export the public copy */
+    if ((err = ecc_make_key(prng, wprng, ecc_get_size(key), &pubkey)) != CRYPT_OK) {
+       return err;
+    }
+
+    pubkeysize = (unsigned long)sizeof(pub_expt);
+    if ((err = ecc_export(pub_expt, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
+       ecc_free(&pubkey);
+       return err;
+    }
+    
+    /* now check if the out buffer is big enough */
+    if (*len < (9 + PACKET_SIZE + pubkeysize + hash_descriptor[hash].hashsize)) {
+       ecc_free(&pubkey);
+       return CRYPT_BUFFER_OVERFLOW;
+    }
+
+    /* make random key */
+    hashsize  = hash_descriptor[hash].hashsize;
+    x = (unsigned long)sizeof(ecc_shared);
+    if ((err = ecc_shared_secret(&pubkey, key, ecc_shared, &x)) != CRYPT_OK) {
+       ecc_free(&pubkey);
+       return err;
+    }
+    ecc_free(&pubkey);
+    z = (unsigned long)sizeof(skey);
+    if ((err = hash_memory(hash, ecc_shared, x, skey, &z)) != CRYPT_OK) {
+       return err;
+    }
+    
+    /* store header */
+    packet_store_header(out, PACKET_SECT_ECC, PACKET_SUB_ENC_KEY);    
+
+    /* output header */
+    y = PACKET_SIZE;
+ 
+    /* size of hash name and the name itself */
+    out[y++] = hash_descriptor[hash].ID;
+
+    /* length of ECC pubkey and the key itself */
+    STORE32L(pubkeysize, out+y);
+    y += 4;
+
+    for (x = 0; x < pubkeysize; x++, y++) {
+        out[y] = pub_expt[x];
+    }
+
+    STORE32L(keylen, out+y);
+    y += 4;
+
+    /* Encrypt/Store the encrypted key */
+    for (x = 0; x < keylen; x++, y++) {
+      out[y] = skey[x] ^ inkey[x];
+    }
+    *len = y;
+
+#ifdef CLEAN_STACK
+    /* clean up */
+    zeromem(pub_expt, sizeof(pub_expt));
+    zeromem(ecc_shared, sizeof(ecc_shared));
+    zeromem(skey, sizeof(skey));
+#endif
+    return CRYPT_OK;
+}
+
+int ecc_decrypt_key(const unsigned char *in, unsigned long inlen,
+                          unsigned char *outkey, unsigned long *keylen, 
+                          ecc_key *key)
+{
+   unsigned char shared_secret[256], skey[MAXBLOCKSIZE];
+   unsigned long x, y, z, hashsize, keysize;
+   int hash, err;
+   ecc_key pubkey;
+
+   _ARGCHK(in     != NULL);
+   _ARGCHK(outkey != NULL);
+   _ARGCHK(keylen != NULL);
+   _ARGCHK(key    != NULL);
+
+   /* right key type? */
+   if (key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+   
+   /* correct length ? */
+   if (inlen < PACKET_SIZE+1+4+4) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      inlen -= PACKET_SIZE+1+4+4;
+   }
+
+   /* is header correct? */
+   if ((err = packet_valid_header((unsigned char *)in, PACKET_SECT_ECC, PACKET_SUB_ENC_KEY)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* now lets get the hash name */
+   y = PACKET_SIZE;
+   hash = find_hash_id(in[y++]);
+   if (hash == -1) {
+      return CRYPT_INVALID_HASH;
+   }
+
+   /* common values */
+   hashsize  = hash_descriptor[hash].hashsize;
+
+   /* get public key */
+   LOAD32L(x, in+y);
+   if (inlen < x) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      inlen -= x;
+   }
+   y += 4;
+   if ((err = ecc_import(in+y, x, &pubkey)) != CRYPT_OK) {
+      return err;
+   }
+   y += x;
+
+   /* make shared key */
+   x = (unsigned long)sizeof(shared_secret);
+   if ((err = ecc_shared_secret(key, &pubkey, shared_secret, &x)) != CRYPT_OK) {
+      ecc_free(&pubkey);
+      return err;
+   }
+   ecc_free(&pubkey);
+
+   z = (unsigned long)sizeof(skey);
+   if ((err = hash_memory(hash, shared_secret, x, skey, &z)) != CRYPT_OK) {
+      return err;
+   }
+
+   LOAD32L(keysize, in+y);
+   if (inlen < keysize) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      inlen -= keysize;
+   }
+   y += 4;
+
+   if (*keylen < keysize) {
+       err = CRYPT_BUFFER_OVERFLOW;
+       goto done;
+   }
+
+   /* Decrypt the key */
+   for (x = 0; x < keysize; x++, y++) {
+     outkey[x] = skey[x] ^ in[y];
+   }
+
+   *keylen = keysize;
+
+   err = CRYPT_OK;
+done:
+#ifdef CLEAN_STACK
+   zeromem(shared_secret, sizeof(shared_secret));
+   zeromem(skey, sizeof(skey));
+#endif
+   return err;
+}
+
+int ecc_sign_hash(const unsigned char *in,  unsigned long inlen, 
+                        unsigned char *out, unsigned long *outlen, 
+                        prng_state *prng, int wprng, ecc_key *key)
+{
+   ecc_key pubkey;
+   mp_int b, p;
+   unsigned char epubkey[256], er[256];
+   unsigned long x, y, pubkeysize, rsize;
+   int  err;
+
+   _ARGCHK(in     != NULL);
+   _ARGCHK(out    != NULL);
+   _ARGCHK(outlen != NULL);
+   _ARGCHK(key    != NULL);
+
+   /* is this a private key? */
+   if (key->type != PK_PRIVATE) {
+      return CRYPT_PK_NOT_PRIVATE;
+   }
+   
+   /* is the IDX valid ?  */
+   if (is_valid_idx(key->idx) != 1) {
+      return CRYPT_PK_INVALID_TYPE;
+   }
+   
+   if ((err = prng_is_valid(wprng)) != CRYPT_OK) {
+      return err;
+   }
+
+   /* make up a key and export the public copy */
+   if ((err = ecc_make_key(prng, wprng, ecc_get_size(key), &pubkey)) != CRYPT_OK) {
+      return err;
+   }
+
+   pubkeysize = (unsigned long)sizeof(epubkey);
+   if ((err = ecc_export(epubkey, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
+      ecc_free(&pubkey);
+      return err;
+   }
+
+   /* get the hash and load it as a bignum into 'b' */
+   /* init the bignums */
+   if ((err = mp_init_multi(&b, &p, NULL)) != MP_OKAY) { 
+      ecc_free(&pubkey);
+      return mpi_to_ltc_error(err);
+   }
+   if ((err = mp_read_radix(&p, (char *)sets[key->idx].order, 64)) != MP_OKAY)        { goto error; }
+   if ((err = mp_read_unsigned_bin(&b, (unsigned char *)in, (int)inlen)) != MP_OKAY)  { goto error; }
+
+   /* find b = (m - x)/k */
+   if ((err = mp_invmod(&pubkey.k, &p, &pubkey.k)) != MP_OKAY)            { goto error; } /* k = 1/k */
+   if ((err = mp_submod(&b, &key->k, &p, &b)) != MP_OKAY)                 { goto error; } /* b = m - x */
+   if ((err = mp_mulmod(&b, &pubkey.k, &p, &b)) != MP_OKAY)               { goto error; } /* b = (m - x)/k */
+
+   /* export it */
+   rsize = (unsigned long)mp_unsigned_bin_size(&b);
+   if (rsize > (unsigned long)sizeof(er)) { 
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto error; 
+   }
+   if ((err = mp_to_unsigned_bin(&b, er)) != MP_OKAY)                     { goto error; }
+
+   /* now lets check the outlen before we write */
+   if (*outlen < (12 + rsize + pubkeysize)) {
+      err = CRYPT_BUFFER_OVERFLOW;
+      goto done;
+   }
+
+   /* lets output */
+   y = PACKET_SIZE;
+   
+   /* size of public key */
+   STORE32L(pubkeysize, out+y);
+   y += 4;
+
+   /* copy the public key */
+   for (x = 0; x < pubkeysize; x++, y++) {
+       out[y] = epubkey[x];
+   }
+
+   /* size of 'r' */
+   STORE32L(rsize, out+y);
+   y += 4;
+
+   /* copy r */
+   for (x = 0; x < rsize; x++, y++) {
+       out[y] = er[x];
+   }
+
+   /* store header */
+   packet_store_header(out, PACKET_SECT_ECC, PACKET_SUB_SIGNED);
+
+   /* clear memory */
+   *outlen = y;
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+done:
+   mp_clear_multi(&b, &p, NULL);
+   ecc_free(&pubkey);
+#ifdef CLEAN_STACK
+   zeromem(er, sizeof(er));
+   zeromem(epubkey, sizeof(epubkey));
+#endif
+   return err;   
+}
+
+/* verify that mG = (bA + Y)
+ *
+ * The signatures work by making up a fresh key "a" with a public key "A".  Now we want to sign so the 
+ * public key Y = xG can verify it.
+ *
+ * b = (m - x)/k, A is the public key embedded and Y is the users public key [who signed it]
+ * A = kG therefore bA == ((m-x)/k)kG == (m-x)G
+ *
+ * Adding Y = xG to the bA gives us (m-x)G + xG == mG
+ *
+ * The user given only xG, kG and b cannot determine k or x which means they can't find the private key.
+ * 
+ */
+int ecc_verify_hash(const unsigned char *sig, unsigned long siglen,
+                    const unsigned char *hash, unsigned long inlen, 
+                    int *stat, ecc_key *key)
+{
+   ecc_point *mG;
+   ecc_key   pubkey;
+   mp_int b, p, m, mu;
+   unsigned long x, y;
+   int err;
+
+   _ARGCHK(sig  != NULL);
+   _ARGCHK(hash != NULL);
+   _ARGCHK(stat != NULL);
+   _ARGCHK(key  != NULL);
+
+   /* default to invalid signature */
+   *stat = 0;
+
+   if (siglen < PACKET_SIZE+4+4) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      siglen -= PACKET_SIZE+4+4;
+   }
+
+   /* is the message format correct? */
+   if ((err = packet_valid_header((unsigned char *)sig, PACKET_SECT_ECC, PACKET_SUB_SIGNED)) != CRYPT_OK) {
+      return err;
+   }     
+
+   /* get hash name */
+   y = PACKET_SIZE;
+
+   /* get size of public key */
+   LOAD32L(x, sig+y);
+   if (siglen < x) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      siglen -= x;
+   }
+   y += 4;
+
+   /* load the public key */
+   if ((err = ecc_import((unsigned char*)sig+y, x, &pubkey)) != CRYPT_OK) {
+      return err;
+   }
+   y += x;
+
+   /* load size of 'b' */
+   LOAD32L(x, sig+y);
+   if (siglen < x) {
+      return CRYPT_INVALID_PACKET;
+   } else {
+      siglen -= x;
+   }
+   y += 4;
+
+   /* init values */
+   if ((err = mp_init_multi(&b, &m, &p, &mu, NULL)) != MP_OKAY) { 
+      ecc_free(&pubkey);
+      return mpi_to_ltc_error(err);
+   }
+
+   mG = new_point();
+   if (mG == NULL) { 
+      mp_clear_multi(&b, &m, &p, &mu, NULL);
+      ecc_free(&pubkey);
+      return CRYPT_MEM;
+   } 
+
+   /* load b */
+   if ((err = mp_read_unsigned_bin(&b, (unsigned char *)sig+y, (int)x)) != MP_OKAY)        { goto error; }
+   y += x;
+
+   /* get m in binary a bignum */
+   if ((err = mp_read_unsigned_bin(&m, (unsigned char *)hash, (int)inlen)) != MP_OKAY)     { goto error; }
+   
+   /* load prime */
+   if ((err = mp_read_radix(&p, (char *)sets[key->idx].prime, 64)) != MP_OKAY)             { goto error; }
+   
+   /* calculate barrett stuff */
+   mp_set(&mu, 1); 
+   mp_lshd(&mu, 2 * USED(&p));
+   if ((err = mp_div(&mu, &p, &mu, NULL)) != MP_OKAY)                                      { goto error; }
+
+   /* get bA */
+   if ((err = ecc_mulmod(&b, &pubkey.pubkey, &pubkey.pubkey, &p)) != CRYPT_OK)                  { goto done; }
+   
+   /* get bA + Y */
+   if ((err = add_point(&pubkey.pubkey, &key->pubkey, &pubkey.pubkey, &p, &mu)) != CRYPT_OK)    { goto done; }
+
+   /* get mG */
+   if ((err = mp_read_radix(&mG->x, (char *)sets[key->idx].Gx, 64)) != MP_OKAY)                 { goto error; }
+   if ((err = mp_read_radix(&mG->y, (char *)sets[key->idx].Gy, 64)) != MP_OKAY)                 { goto error; }
+   if ((err = ecc_mulmod(&m, mG, mG, &p)) != CRYPT_OK)                                          { goto done; }
+
+   /* compare mG to bA + Y */
+   if (mp_cmp(&mG->x, &pubkey.pubkey.x) == MP_EQ && mp_cmp(&mG->y, &pubkey.pubkey.y) == MP_EQ) {
+      *stat = 1;
+   }
+
+   /* clear up and return */
+   err = CRYPT_OK;
+   goto done;
+error:
+   err = mpi_to_ltc_error(err);
+done:
+   del_point(mG);
+   ecc_free(&pubkey);
+   mp_clear_multi(&p, &m, &b, &mu, NULL);
+   return err;
+}
+