--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pk/ecc/ecc_sys.c	Sun May 08 06:36:47 2005 +0000
@@ -0,0 +1,548 @@
+/* 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
+ */
+
+/**
+  @file ecc_sys.c
+  ECC Crypto, Tom St Denis
+*/
+  
+/**
+  Encrypt a symmetric key with ECC 
+  @param in         The symmetric key you want to encrypt
+  @param inlen      The length of the key to encrypt (octets)
+  @param out        [out] The destination for the ciphertext
+  @param outlen     [in/out] The max size and resulting size of the ciphertext
+  @param prng       An active PRNG state
+  @param wprng      The index of the PRNG you wish to use 
+  @param hash       The index of the hash you want to use 
+  @param key        The ECC key you want to encrypt to
+  @return CRYPT_OK if successful
+*/
+int ecc_encrypt_key(const unsigned char *in,   unsigned long inlen,
+                          unsigned char *out,  unsigned long *outlen, 
+                          prng_state *prng, int wprng, int hash, 
+                          ecc_key *key)
+{
+    unsigned char *pub_expt, *ecc_shared, *skey;
+    ecc_key        pubkey;
+    unsigned long  x, y, z, hashsize, pubkeysize;
+    int            err;
+
+    LTC_ARGCHK(in      != NULL);
+    LTC_ARGCHK(out     != NULL);
+    LTC_ARGCHK(outlen  != NULL);
+    LTC_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 (inlen > 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;
+    }
+
+    pub_expt   = XMALLOC(ECC_BUF_SIZE);
+    ecc_shared = XMALLOC(ECC_BUF_SIZE);
+    skey       = XMALLOC(MAXBLOCKSIZE);
+    if (pub_expt == NULL || ecc_shared == NULL || skey == NULL) {
+       if (pub_expt != NULL) {
+          XFREE(pub_expt);
+       }
+       if (ecc_shared != NULL) {
+          XFREE(ecc_shared);
+       }
+       if (skey != NULL) {
+          XFREE(skey);
+       }
+       ecc_free(&pubkey);
+       return CRYPT_MEM;
+    }
+
+    pubkeysize = ECC_BUF_SIZE;
+    if ((err = ecc_export(pub_expt, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
+       ecc_free(&pubkey);
+       goto LBL_ERR;
+    }
+    
+    /* now check if the out buffer is big enough */
+    if (*outlen < (9 + PACKET_SIZE + pubkeysize + hash_descriptor[hash].hashsize)) {
+       ecc_free(&pubkey);
+       err = CRYPT_BUFFER_OVERFLOW;
+       goto LBL_ERR;
+    }
+
+    /* make random key */
+    hashsize  = hash_descriptor[hash].hashsize;
+    x = ECC_BUF_SIZE;
+    if ((err = ecc_shared_secret(&pubkey, key, ecc_shared, &x)) != CRYPT_OK) {
+       ecc_free(&pubkey);
+       goto LBL_ERR;
+    }
+    ecc_free(&pubkey);
+    z = MAXBLOCKSIZE;
+    if ((err = hash_memory(hash, ecc_shared, x, skey, &z)) != CRYPT_OK) {
+       goto LBL_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(inlen, out+y);
+    y += 4;
+
+    /* Encrypt/Store the encrypted key */
+    for (x = 0; x < inlen; x++, y++) {
+      out[y] = skey[x] ^ in[x];
+    }
+    *outlen = y;
+
+    err = CRYPT_OK;
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+    /* clean up */
+    zeromem(pub_expt,   ECC_BUF_SIZE);
+    zeromem(ecc_shared, ECC_BUF_SIZE);
+    zeromem(skey,       MAXBLOCKSIZE);
+#endif
+
+    XFREE(skey);
+    XFREE(ecc_shared);
+    XFREE(pub_expt);
+
+    return err;
+}
+
+/**
+  Decrypt an ECC encrypted key
+  @param in       The ciphertext
+  @param inlen    The length of the ciphertext (octets)
+  @param out      [out] The plaintext
+  @param outlen   [in/out] The max size and resulting size of the plaintext
+  @param key      The corresponding private ECC key
+  @return CRYPT_OK if successful
+*/
+int ecc_decrypt_key(const unsigned char *in,  unsigned long  inlen,
+                          unsigned char *out, unsigned long *outlen, 
+                          ecc_key *key)
+{
+   unsigned char *shared_secret, *skey;
+   unsigned long  x, y, z, hashsize, keysize;
+   int            hash, err;
+   ecc_key        pubkey;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_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;
+
+   /* allocate memory */
+   shared_secret = XMALLOC(ECC_BUF_SIZE);
+   skey          = XMALLOC(MAXBLOCKSIZE);
+   if (shared_secret == NULL || skey == NULL) {
+      if (shared_secret != NULL) {
+         XFREE(shared_secret);
+      }
+      if (skey != NULL) {
+         XFREE(skey);
+      }
+      ecc_free(&pubkey);
+      return CRYPT_MEM;
+   }
+
+   /* make shared key */
+   x = ECC_BUF_SIZE;
+   if ((err = ecc_shared_secret(key, &pubkey, shared_secret, &x)) != CRYPT_OK) {
+      ecc_free(&pubkey);
+      goto LBL_ERR;
+   }
+   ecc_free(&pubkey);
+
+   z = MAXBLOCKSIZE;
+   if ((err = hash_memory(hash, shared_secret, x, skey, &z)) != CRYPT_OK) {
+      goto LBL_ERR;
+   }
+
+   LOAD32L(keysize, in+y);
+   if (inlen < keysize) {
+      err = CRYPT_INVALID_PACKET;
+      goto LBL_ERR;
+   } else {
+      inlen -= keysize;
+   }
+   y += 4;
+
+   if (*outlen < keysize) {
+       err = CRYPT_BUFFER_OVERFLOW;
+       goto LBL_ERR;
+   }
+
+   /* Decrypt the key */
+   for (x = 0; x < keysize; x++, y++) {
+     out[x] = skey[x] ^ in[y];
+   }
+
+   *outlen = keysize;
+
+   err = CRYPT_OK;
+LBL_ERR:
+#ifdef LTC_CLEAN_STACK
+   zeromem(shared_secret, ECC_BUF_SIZE);
+   zeromem(skey,          MAXBLOCKSIZE);
+#endif
+
+   XFREE(skey);
+   XFREE(shared_secret);
+
+   return err;
+}
+
+/**
+  Sign a message digest
+  @param in        The message digest to sign
+  @param inlen     The length of the digest
+  @param out       [out] The destination for 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 you wish to use
+  @param key       A private ECC key
+  @return CRYPT_OK if successful
+*/
+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, *er;
+   unsigned long x, y, pubkeysize, rsize;
+   int           err;
+
+   LTC_ARGCHK(in     != NULL);
+   LTC_ARGCHK(out    != NULL);
+   LTC_ARGCHK(outlen != NULL);
+   LTC_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;
+   }
+
+   /* allocate ram */
+   epubkey = XMALLOC(ECC_BUF_SIZE);
+   er      = XMALLOC(ECC_BUF_SIZE);
+   if (epubkey == NULL || er == NULL) {
+      if (epubkey != NULL) {
+         XFREE(epubkey);
+      }
+      if (er != NULL) {
+         XFREE(er);
+      }
+      ecc_free(&pubkey);
+      return CRYPT_MEM;
+   }
+
+   pubkeysize = ECC_BUF_SIZE;
+   if ((err = ecc_export(epubkey, &pubkeysize, PK_PUBLIC, &pubkey)) != CRYPT_OK) {
+      ecc_free(&pubkey);
+      goto LBL_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);
+      err = mpi_to_ltc_error(err);
+      goto LBL_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 > ECC_BUF_SIZE) { 
+      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 LBL_ERR;
+   }
+
+   /* 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);
+   *outlen = y;
+
+   /* all ok */
+   err = CRYPT_OK;
+   goto LBL_ERR;
+error:
+   err = mpi_to_ltc_error(err);
+LBL_ERR:
+   mp_clear_multi(&b, &p, NULL);
+   ecc_free(&pubkey);
+#ifdef LTC_CLEAN_STACK
+   zeromem(er,      ECC_BUF_SIZE);
+   zeromem(epubkey, ECC_BUF_SIZE);
+#endif
+
+   XFREE(epubkey);
+   XFREE(er);
+
+   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.
+ * 
+ */
+
+/**
+   Verify an ECC signature
+   @param sig         The signature to verify
+   @param siglen      The length of the signature (octets)
+   @param hash        The hash (message digest) that was signed
+   @param hashlen     The length of the hash (octets)
+   @param stat        Result of signature, 1==valid, 0==invalid
+   @param key         The corresponding public ECC key
+   @return CRYPT_OK if successful (even if the signature is not valid)
+*/
+int ecc_verify_hash(const unsigned char *sig,  unsigned long siglen,
+                    const unsigned char *hash, unsigned long hashlen, 
+                    int *stat, ecc_key *key)
+{
+   ecc_point    *mG;
+   ecc_key       pubkey;
+   mp_int        b, p, m, mu;
+   unsigned long x, y;
+   int           err;
+
+   LTC_ARGCHK(sig  != NULL);
+   LTC_ARGCHK(hash != NULL);
+   LTC_ARGCHK(stat != NULL);
+   LTC_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)hashlen)) != 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; }
+
+   /* we have to transform it */
+   if ((err = ecc_map(&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; }
+   mp_set(&mG->z, 1);
+   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;
+}
+