/* 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_verify_hash.c  ECC Crypto, Tom St Denis*/  #ifdef MECC/* verify  * * w  = s^-1 mod n * u1 = xw  * u2 = rw * X = u1*G + u2*Q * v = X_x1 mod n * accept if v == r *//**   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, *mQ;   void          *r, *s, *v, *w, *u1, *u2, *e, *p, *m;   void          *mp;   int           err;   LTC_ARGCHK(sig  != NULL);   LTC_ARGCHK(hash != NULL);   LTC_ARGCHK(stat != NULL);   LTC_ARGCHK(key  != NULL);   /* default to invalid signature */   *stat = 0;   mp    = NULL;   /* is the IDX valid ?  */   if (ltc_ecc_is_valid_idx(key->idx) != 1) {      return CRYPT_PK_INVALID_TYPE;   }   /* allocate ints */   if ((err = mp_init_multi(&r, &s, &v, &w, &u1, &u2, &p, &e, &m, NULL)) != CRYPT_OK) {      return CRYPT_MEM;   }   /* allocate points */   mG = ltc_ecc_new_point();   mQ = ltc_ecc_new_point();   if (mQ  == NULL || mG == NULL) {      err = CRYPT_MEM;      goto error;   }   /* parse header */   if ((err = der_decode_sequence_multi(sig, siglen,                                  LTC_ASN1_INTEGER, 1UL, r,                                  LTC_ASN1_INTEGER, 1UL, s,                                  LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) {      goto error;   }   /* get the order */   if ((err = mp_read_radix(p, (char *)key->dp->order, 16)) != CRYPT_OK)                                { goto error; }   /* get the modulus */   if ((err = mp_read_radix(m, (char *)key->dp->prime, 16)) != CRYPT_OK)                                { goto error; }   /* check for zero */   if (mp_iszero(r) || mp_iszero(s) || mp_cmp(r, p) != LTC_MP_LT || mp_cmp(s, p) != LTC_MP_LT) {      err = CRYPT_INVALID_PACKET;      goto error;   }   /* read hash */   if ((err = mp_read_unsigned_bin(e, (unsigned char *)hash, (int)hashlen)) != CRYPT_OK)                { goto error; }   /*  w  = s^-1 mod n */   if ((err = mp_invmod(s, p, w)) != CRYPT_OK)                                                          { goto error; }   /* u1 = ew */   if ((err = mp_mulmod(e, w, p, u1)) != CRYPT_OK)                                                      { goto error; }   /* u2 = rw */   if ((err = mp_mulmod(r, w, p, u2)) != CRYPT_OK)                                                      { goto error; }   /* find mG and mQ */   if ((err = mp_read_radix(mG->x, (char *)key->dp->Gx, 16)) != CRYPT_OK)                               { goto error; }   if ((err = mp_read_radix(mG->y, (char *)key->dp->Gy, 16)) != CRYPT_OK)                               { goto error; }   if ((err = mp_set(mG->z, 1)) != CRYPT_OK)                                                            { goto error; }   if ((err = mp_copy(key->pubkey.x, mQ->x)) != CRYPT_OK)                                               { goto error; }   if ((err = mp_copy(key->pubkey.y, mQ->y)) != CRYPT_OK)                                               { goto error; }   if ((err = mp_copy(key->pubkey.z, mQ->z)) != CRYPT_OK)                                               { goto error; }   /* compute u1*mG + u2*mQ = mG */   if (ltc_mp.ecc_mul2add == NULL) {      if ((err = ltc_mp.ecc_ptmul(u1, mG, mG, m, 0)) != CRYPT_OK)                                       { goto error; }      if ((err = ltc_mp.ecc_ptmul(u2, mQ, mQ, m, 0)) != CRYPT_OK)                                       { goto error; }        /* find the montgomery mp */      if ((err = mp_montgomery_setup(m, &mp)) != CRYPT_OK)                                              { goto error; }      /* add them */      if ((err = ltc_mp.ecc_ptadd(mQ, mG, mG, m, mp)) != CRYPT_OK)                                      { goto error; }         /* reduce */      if ((err = ltc_mp.ecc_map(mG, m, mp)) != CRYPT_OK)                                                { goto error; }   } else {      /* use Shamir's trick to compute u1*mG + u2*mQ using half of the doubles */      if ((err = ltc_mp.ecc_mul2add(mG, u1, mQ, u2, mG, m)) != CRYPT_OK)                                { goto error; }   }   /* v = X_x1 mod n */   if ((err = mp_mod(mG->x, p, v)) != CRYPT_OK)                                                         { goto error; }   /* does v == r */   if (mp_cmp(v, r) == LTC_MP_EQ) {      *stat = 1;   }   /* clear up and return */   err = CRYPT_OK;error:   ltc_ecc_del_point(mG);   ltc_ecc_del_point(mQ);   mp_clear_multi(r, s, v, w, u1, u2, p, e, m, NULL);   if (mp != NULL) {       mp_montgomery_free(mp);   }   return err;}#endif/* $Source: /cvs/libtom/libtomcrypt/src/pk/ecc/ecc_verify_hash.c,v $ *//* $Revision: 1.12 $ *//* $Date: 2006/12/04 05:07:59 $ */