/* 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_import.c  ECC Crypto, Tom St Denis*/  #ifdef MECCstatic int is_point(ecc_key *key){   void *prime, *b, *t1, *t2;   int err;      if ((err = mp_init_multi(&prime, &b, &t1, &t2, NULL)) != CRYPT_OK) {      return err;   }      /* load prime and b */   if ((err = mp_read_radix(prime, key->dp->prime, 16)) != CRYPT_OK)                          { goto error; }   if ((err = mp_read_radix(b, key->dp->B, 16)) != CRYPT_OK)                                  { goto error; }      /* compute y^2 */   if ((err = mp_sqr(key->pubkey.y, t1)) != CRYPT_OK)                                         { goto error; }      /* compute x^3 */   if ((err = mp_sqr(key->pubkey.x, t2)) != CRYPT_OK)                                         { goto error; }   if ((err = mp_mod(t2, prime, t2)) != CRYPT_OK)                                             { goto error; }   if ((err = mp_mul(key->pubkey.x, t2, t2)) != CRYPT_OK)                                     { goto error; }      /* compute y^2 - x^3 */   if ((err = mp_sub(t1, t2, t1)) != CRYPT_OK)                                                { goto error; }      /* compute y^2 - x^3 + 3x */   if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK)                                     { goto error; }   if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK)                                     { goto error; }   if ((err = mp_add(t1, key->pubkey.x, t1)) != CRYPT_OK)                                     { goto error; }   if ((err = mp_mod(t1, prime, t1)) != CRYPT_OK)                                             { goto error; }   while (mp_cmp_d(t1, 0) == LTC_MP_LT) {      if ((err = mp_add(t1, prime, t1)) != CRYPT_OK)                                          { goto error; }   }   while (mp_cmp(t1, prime) != LTC_MP_LT) {      if ((err = mp_sub(t1, prime, t1)) != CRYPT_OK)                                          { goto error; }   }      /* compare to b */   if (mp_cmp(t1, b) != LTC_MP_EQ) {      err = CRYPT_INVALID_PACKET;   } else {      err = CRYPT_OK;   }   error:   mp_clear_multi(prime, b, t1, t2, NULL);   return err;}/**  Import an ECC key from a binary packet  @param in      The packet to import  @param inlen   The length of the packet  @param key     [out] The destination of the import  @return CRYPT_OK if successful, upon error all allocated memory will be freed*/int ecc_import(const unsigned char *in, unsigned long inlen, ecc_key *key){   return ecc_import_ex(in, inlen, key, NULL);}/**  Import an ECC key from a binary packet, using user supplied domain params rather than one of the NIST ones  @param in      The packet to import  @param inlen   The length of the packet  @param key     [out] The destination of the import  @param dp      pointer to user supplied params; must be the same as the params used when exporting  @return CRYPT_OK if successful, upon error all allocated memory will be freed*/int ecc_import_ex(const unsigned char *in, unsigned long inlen, ecc_key *key, const ltc_ecc_set_type *dp){   unsigned long key_size;   unsigned char flags[1];   int           err;   LTC_ARGCHK(in  != NULL);   LTC_ARGCHK(key != NULL);   LTC_ARGCHK(ltc_mp.name != NULL);   /* init key */   if (mp_init_multi(&key->pubkey.x, &key->pubkey.y, &key->pubkey.z, &key->k, NULL) != CRYPT_OK) {      return CRYPT_MEM;   }   /* find out what type of key it is */   if ((err = der_decode_sequence_multi(in, inlen,                                   LTC_ASN1_BIT_STRING, 1UL, &flags,                                  LTC_ASN1_EOL,        0UL, NULL)) != CRYPT_OK) {      goto done;   }   if (flags[0] == 1) {      /* private key */      key->type = PK_PRIVATE;      if ((err = der_decode_sequence_multi(in, inlen,                                     LTC_ASN1_BIT_STRING,      1UL, flags,                                     LTC_ASN1_SHORT_INTEGER,   1UL, &key_size,                                     LTC_ASN1_INTEGER,         1UL, key->pubkey.x,                                     LTC_ASN1_INTEGER,         1UL, key->pubkey.y,                                     LTC_ASN1_INTEGER,         1UL, key->k,                                     LTC_ASN1_EOL,             0UL, NULL)) != CRYPT_OK) {         goto done;      }   } else {      /* public key */      key->type = PK_PUBLIC;      if ((err = der_decode_sequence_multi(in, inlen,                                     LTC_ASN1_BIT_STRING,      1UL, flags,                                     LTC_ASN1_SHORT_INTEGER,   1UL, &key_size,                                     LTC_ASN1_INTEGER,         1UL, key->pubkey.x,                                     LTC_ASN1_INTEGER,         1UL, key->pubkey.y,                                     LTC_ASN1_EOL,             0UL, NULL)) != CRYPT_OK) {         goto done;      }   }   if (dp == NULL) {     /* find the idx */     for (key->idx = 0; ltc_ecc_sets[key->idx].size && (unsigned long)ltc_ecc_sets[key->idx].size != key_size; ++key->idx);     if (ltc_ecc_sets[key->idx].size == 0) {       err = CRYPT_INVALID_PACKET;       goto done;     }     key->dp = &ltc_ecc_sets[key->idx];   } else {     key->idx = -1;     key->dp = dp;   }   /* set z */   if ((err = mp_set(key->pubkey.z, 1)) != CRYPT_OK) { goto done; }      /* is it a point on the curve?  */   if ((err = is_point(key)) != CRYPT_OK) {      goto done;   }   /* we're good */   return CRYPT_OK;done:   mp_clear_multi(key->pubkey.x, key->pubkey.y, key->pubkey.z, key->k, NULL);   return err;}#endif/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_import.c,v $ *//* $Revision: 1.11 $ *//* $Date: 2006/12/04 02:19:48 $ */