text: // Copyright (c) 2009-2012 The Ferretcoin developers
  // Copyright (c) 2011-2012 Litecoin Developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <map>
  
  #include <openssl/ecdsa.h>
  #include <openssl/obj_mac.h>
  
  #include "key.h"
  
  // Generate a private key from just the secret parameter
  int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
  {
      int ok = 0;
      BN_CTX *ctx = NULL;
      EC_POINT *pub_key = NULL;
  
      if (!eckey) return 0;
  
      const EC_GROUP *group = EC_KEY_get0_group(eckey);
  
      if ((ctx = BN_CTX_new()) == NULL)
          goto err;
  
      pub_key = EC_POINT_new(group);
  
      if (pub_key == NULL)
          goto err;
  
      if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
          goto err;
  
      EC_KEY_set_private_key(eckey,priv_key);
      EC_KEY_set_public_key(eckey,pub_key);
  
      ok = 1;
  
  err:
  
      if (pub_key)
          EC_POINT_free(pub_key);
      if (ctx != NULL)
          BN_CTX_free(ctx);
  
      return(ok);
  }
  
  // Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
  // recid selects which key is recovered
  // if check is nonzero, additional checks are performed
  int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
  {
      if (!eckey) return 0;
  
      int ret = 0;
      BN_CTX *ctx = NULL;
  
      BIGNUM *x = NULL;
      BIGNUM *e = NULL;
      BIGNUM *order = NULL;
      BIGNUM *sor = NULL;
      BIGNUM *eor = NULL;
      BIGNUM *field = NULL;
      EC_POINT *R = NULL;
      EC_POINT *O = NULL;
      EC_POINT *Q = NULL;
      BIGNUM *rr = NULL;
      BIGNUM *zero = NULL;
      int n = 0;
      int i = recid / 2;
  
      const EC_GROUP *group = EC_KEY_get0_group(eckey);
      if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
      BN_CTX_start(ctx);
      order = BN_CTX_get(ctx);
      if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
      x = BN_CTX_get(ctx);
      if (!BN_copy(x, order)) { ret=-1; goto err; }
      if (!BN_mul_word(x, i)) { ret=-1; goto err; }
      if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
      field = BN_CTX_get(ctx);
      if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
      if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
      if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
      if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
      if (check)
      {
          if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
          if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
          if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
      }
      if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
      n = EC_GROUP_get_degree(group);
      e = BN_CTX_get(ctx);
      if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
      if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
      zero = BN_CTX_get(ctx);
      if (!BN_zero(zero)) { ret=-1; goto err; }
      if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
      rr = BN_CTX_get(ctx);
      if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
      sor = BN_CTX_get(ctx);
      if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
      eor = BN_CTX_get(ctx);
      if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
      if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
      if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
  
      ret = 1;
  
  err:
      if (ctx) {
          BN_CTX_end(ctx);
          BN_CTX_free(ctx);
      }
      if (R != NULL) EC_POINT_free(R);
      if (O != NULL) EC_POINT_free(O);
      if (Q != NULL) EC_POINT_free(Q);
      return ret;
  }
  
  void CKey::SetCompressedPubKey()
  {
      EC_KEY_set_conv_form(pkey, POINT_CONVERSION_COMPRESSED);
      fCompressedPubKey = true;
  }
  
  void CKey::Reset()
  {
      fCompressedPubKey = false;
      if (pkey != NULL)
          EC_KEY_free(pkey);
      pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
      if (pkey == NULL)
          throw key_error("CKey::CKey() : EC_KEY_new_by_curve_name failed");
      fSet = false;
  }
  
  CKey::CKey()
  {
      pkey = NULL;
      Reset();
  }
  
  CKey::CKey(const CKey& b)
  {
      pkey = EC_KEY_dup(b.pkey);
      if (pkey == NULL)
          throw key_error("CKey::CKey(const CKey&) : EC_KEY_dup failed");
      fSet = b.fSet;
  }
  
  CKey& CKey::operator=(const CKey& b)
  {
      if (!EC_KEY_copy(pkey, b.pkey))
          throw key_error("CKey::operator=(const CKey&) : EC_KEY_copy failed");
      fSet = b.fSet;
      return (*this);
  }
  
  CKey::~CKey()
  {
      EC_KEY_free(pkey);
  }
  
  bool CKey::IsNull() const
  {
      return !fSet;
  }
  
  bool CKey::IsCompressed() const
  {
      return fCompressedPubKey;
  }
  
  void CKey::MakeNewKey(bool fCompressed)
  {
      if (!EC_KEY_generate_key(pkey))
          throw key_error("CKey::MakeNewKey() : EC_KEY_generate_key failed");
      if (fCompressed)
          SetCompressedPubKey();
      fSet = true;
  }
  
  bool CKey::SetPrivKey(const CPrivKey& vchPrivKey)
  {
      const unsigned char* pbegin = &vchPrivKey[0];
      if (!d2i_ECPrivateKey(&pkey, &pbegin, vchPrivKey.size()))
          return false;
      fSet = true;
      return true;
  }
  
  bool CKey::SetSecret(const CSecret& vchSecret, bool fCompressed)
  {
      EC_KEY_free(pkey);
      pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
      if (pkey == NULL)
          throw key_error("CKey::SetSecret() : EC_KEY_new_by_curve_name failed");
      if (vchSecret.size() != 32)
          throw key_error("CKey::SetSecret() : secret must be 32 bytes");
      BIGNUM *bn = BN_bin2bn(&vchSecret[0],32,BN_new());
      if (bn == NULL)
          throw key_error("CKey::SetSecret() : BN_bin2bn failed");
      if (!EC_KEY_regenerate_key(pkey,bn))
      {
          BN_clear_free(bn);
          throw key_error("CKey::SetSecret() : EC_KEY_regenerate_key failed");
      }
      BN_clear_free(bn);
      fSet = true;
      if (fCompressed || fCompressedPubKey)
          SetCompressedPubKey();
      return true;
  }
  
  CSecret CKey::GetSecret(bool &fCompressed) const
  {
      CSecret vchRet;
      vchRet.resize(32);
      const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
      int nBytes = BN_num_bytes(bn);
      if (bn == NULL)
          throw key_error("CKey::GetSecret() : EC_KEY_get0_private_key failed");
      int n=BN_bn2bin(bn,&vchRet[32 - nBytes]);
      if (n != nBytes)
          throw key_error("CKey::GetSecret(): BN_bn2bin failed");
      fCompressed = fCompressedPubKey;
      return vchRet;
  }
  
  CPrivKey CKey::GetPrivKey() const
  {
      int nSize = i2d_ECPrivateKey(pkey, NULL);
      if (!nSize)
          throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey failed");
      CPrivKey vchPrivKey(nSize, 0);
      unsigned char* pbegin = &vchPrivKey[0];
      if (i2d_ECPrivateKey(pkey, &pbegin) != nSize)
          throw key_error("CKey::GetPrivKey() : i2d_ECPrivateKey returned unexpected size");
      return vchPrivKey;
  }
  
  bool CKey::SetPubKey(const CPubKey& vchPubKey)
  {
      const unsigned char* pbegin = &vchPubKey.vchPubKey[0];
      if (!o2i_ECPublicKey(&pkey, &pbegin, vchPubKey.vchPubKey.size()))
          return false;
      fSet = true;
      if (vchPubKey.vchPubKey.size() == 33)
          SetCompressedPubKey();
      return true;
  }
  
  CPubKey CKey::GetPubKey() const
  {
      int nSize = i2o_ECPublicKey(pkey, NULL);
      if (!nSize)
          throw key_error("CKey::GetPubKey() : i2o_ECPublicKey failed");
      std::vector<unsigned char> vchPubKey(nSize, 0);
      unsigned char* pbegin = &vchPubKey[0];
      if (i2o_ECPublicKey(pkey, &pbegin) != nSize)
          throw key_error("CKey::GetPubKey() : i2o_ECPublicKey returned unexpected size");
      return CPubKey(vchPubKey);
  }
  
  bool CKey::Sign(uint256 hash, std::vector<unsigned char>& vchSig)
  {
      unsigned int nSize = ECDSA_size(pkey);
      vchSig.resize(nSize); // Make sure it is big enough
      if (!ECDSA_sign(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], &nSize, pkey))
      {
          vchSig.clear();
          return false;
      }
      vchSig.resize(nSize); // Shrink to fit actual size
      return true;
  }
  
  // create a compact signature (65 bytes), which allows reconstructing the used public key
  // The format is one header byte, followed by two times 32 bytes for the serialized r and s values.
  // The header byte: 0x1B = first key with even y, 0x1C = first key with odd y,
  //                  0x1D = second key with even y, 0x1E = second key with odd y
  bool CKey::SignCompact(uint256 hash, std::vector<unsigned char>& vchSig)
  {
      bool fOk = false;
      ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
      if (sig==NULL)
          return false;
      vchSig.clear();
      vchSig.resize(65,0);
      int nBitsR = BN_num_bits(sig->r);
      int nBitsS = BN_num_bits(sig->s);
      if (nBitsR <= 256 && nBitsS <= 256)
      {
          int nRecId = -1;
          for (int i=0; i<4; i++)
          {
              CKey keyRec;
              keyRec.fSet = true;
              if (fCompressedPubKey)
                  keyRec.SetCompressedPubKey();
              if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1)
                  if (keyRec.GetPubKey() == this->GetPubKey())
                  {
                      nRecId = i;
                      break;
                  }
          }
  
          if (nRecId == -1)
              throw key_error("CKey::SignCompact() : unable to construct recoverable key");
  
          vchSig[0] = nRecId+27+(fCompressedPubKey ? 4 : 0);
          BN_bn2bin(sig->r,&vchSig[33-(nBitsR+7)/8]);
          BN_bn2bin(sig->s,&vchSig[65-(nBitsS+7)/8]);
          fOk = true;
      }
      ECDSA_SIG_free(sig);
      return fOk;
  }
  
  // reconstruct public key from a compact signature
  // This is only slightly more CPU intensive than just verifying it.
  // If this function succeeds, the recovered public key is guaranteed to be valid
  // (the signature is a valid signature of the given data for that key)
  bool CKey::SetCompactSignature(uint256 hash, const std::vector<unsigned char>& vchSig)
  {
      if (vchSig.size() != 65)
          return false;
      int nV = vchSig[0];
      if (nV<27 || nV>=35)
          return false;
      ECDSA_SIG *sig = ECDSA_SIG_new();
      BN_bin2bn(&vchSig[1],32,sig->r);
      BN_bin2bn(&vchSig[33],32,sig->s);
  
      EC_KEY_free(pkey);
      pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
      if (nV >= 31)
      {
          SetCompressedPubKey();
          nV -= 4;
      }
      if (ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), nV - 27, 0) == 1)
      {
          fSet = true;
          ECDSA_SIG_free(sig);
          return true;
      }
      return false;
  }
  
  bool CKey::Verify(uint256 hash, const std::vector<unsigned char>& vchSig)
  {
      // -1 = error, 0 = bad sig, 1 = good
      if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
          return false;
  
      return true;
  }
  
  bool CKey::VerifyCompact(uint256 hash, const std::vector<unsigned char>& vchSig)
  {
      CKey key;
      if (!key.SetCompactSignature(hash, vchSig))
          return false;
      if (GetPubKey() != key.GetPubKey())
          return false;
  
      return true;
  }
  
  bool CKey::IsValid()
  {
      if (!fSet)
          return false;
  
      bool fCompr;
      CSecret secret = GetSecret(fCompr);
      CKey key2;
      key2.SetSecret(secret, fCompr);
      return GetPubKey() == key2.GetPubKey();
  }
  