text: // Copyright (c) 2009-2014 The Bitcoin developers
  // Copyright (c) 2017 The PIVX developers
  // Copyright (c) 2017 The Dividend developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include "key.h"
  
  #include "crypto/hmac_sha512.h"
  #include "crypto/rfc6979_hmac_sha256.h"
  #include "eccryptoverify.h"
  #include "pubkey.h"
  #include "random.h"
  
  #include "ecwrapper.h"
  #include <secp256k1.h>
  
  //! anonymous namespace
  namespace
  {
  class CSecp256k1Init
  {
  public:
      CSecp256k1Init()
      {
          secp256k1_start(SECP256K1_START_SIGN);
      }
      ~CSecp256k1Init()
      {
          secp256k1_stop();
      }
  };
  static CSecp256k1Init instance_of_csecp256k1;
  
  } // anon namespace
  
  bool CKey::Check(const unsigned char* vch)
  {
      return eccrypto::Check(vch);
  }
  
  void CKey::MakeNewKey(bool fCompressedIn)
  {
      do {
          GetRandBytes(vch, sizeof(vch));
      } while (!Check(vch));
      fValid = true;
      fCompressed = fCompressedIn;
  }
  
  bool CKey::SetPrivKey(const CPrivKey& privkey, bool fCompressedIn)
  {
      if (!secp256k1_ec_privkey_import((unsigned char*)begin(), &privkey[0], privkey.size()))
          return false;
      fCompressed = fCompressedIn;
      fValid = true;
      return true;
  }
  
  uint256 CKey::GetPrivKey_256()
  {
      void* key = &vch;
      uint256* key_256 = (uint256*)key;
  
      return *key_256;
  }
  
  CPrivKey CKey::GetPrivKey() const
  {
      assert(fValid);
      CPrivKey privkey;
      int privkeylen, ret;
      privkey.resize(279);
      privkeylen = 279;
      ret = secp256k1_ec_privkey_export(begin(), (unsigned char*)&privkey[0], &privkeylen, fCompressed);
      assert(ret);
      privkey.resize(privkeylen);
      return privkey;
  }
  
  CPubKey CKey::GetPubKey() const
  {
      assert(fValid);
      CPubKey result;
      int clen = 65;
      int ret = secp256k1_ec_pubkey_create((unsigned char*)result.begin(), &clen, begin(), fCompressed);
      assert((int)result.size() == clen);
      assert(ret);
      assert(result.IsValid());
      return result;
  }
  
  bool CKey::Sign(const uint256& hash, std::vector<unsigned char>& vchSig, uint32_t test_case) const
  {
      if (!fValid)
          return false;
      vchSig.resize(72);
      RFC6979_HMAC_SHA256 prng(begin(), 32, (unsigned char*)&hash, 32);
      do {
          uint256 nonce;
          prng.Generate((unsigned char*)&nonce, 32);
          nonce += test_case;
          int nSigLen = 72;
          int ret = secp256k1_ecdsa_sign((const unsigned char*)&hash, 32, (unsigned char*)&vchSig[0], &nSigLen, begin(), (unsigned char*)&nonce);
          nonce = 0;
          if (ret) {
              vchSig.resize(nSigLen);
              return true;
          }
      } while (true);
  }
  
  bool CKey::VerifyPubKey(const CPubKey& pubkey) const
  {
      if (pubkey.IsCompressed() != fCompressed) {
          return false;
      }
      unsigned char rnd[8];
      std::string str = "Bitcoin key verification\n";
      GetRandBytes(rnd, sizeof(rnd));
      uint256 hash;
      CHash256().Write((unsigned char*)str.data(), str.size()).Write(rnd, sizeof(rnd)).Finalize((unsigned char*)&hash);
      std::vector<unsigned char> vchSig;
      Sign(hash, vchSig);
      return pubkey.Verify(hash, vchSig);
  }
  
  bool CKey::SignCompact(const uint256& hash, std::vector<unsigned char>& vchSig) const
  {
      if (!fValid)
          return false;
      vchSig.resize(65);
      int rec = -1;
      RFC6979_HMAC_SHA256 prng(begin(), 32, (unsigned char*)&hash, 32);
      do {
          uint256 nonce;
          prng.Generate((unsigned char*)&nonce, 32);
          int ret = secp256k1_ecdsa_sign_compact((const unsigned char*)&hash, 32, &vchSig[1], begin(), (unsigned char*)&nonce, &rec);
          nonce = 0;
          if (ret)
              break;
      } while (true);
      assert(rec != -1);
      vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
      return true;
  }
  
  bool CKey::Load(CPrivKey& privkey, CPubKey& vchPubKey, bool fSkipCheck = false)
  {
      if (!secp256k1_ec_privkey_import((unsigned char*)begin(), &privkey[0], privkey.size()))
          return false;
      fCompressed = vchPubKey.IsCompressed();
      fValid = true;
  
      if (fSkipCheck)
          return true;
  
      return VerifyPubKey(vchPubKey);
  }
  
  bool CKey::Derive(CKey& keyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const
  {
      assert(IsValid());
      assert(IsCompressed());
      unsigned char out[64];
      LockObject(out);
      if ((nChild >> 31) == 0) {
          CPubKey pubkey = GetPubKey();
          assert(pubkey.begin() + 33 == pubkey.end());
          BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin() + 1, out);
      } else {
          assert(begin() + 32 == end());
          BIP32Hash(cc, nChild, 0, begin(), out);
      }
      memcpy(ccChild, out + 32, 32);
      memcpy((unsigned char*)keyChild.begin(), begin(), 32);
      bool ret = secp256k1_ec_privkey_tweak_add((unsigned char*)keyChild.begin(), out);
      UnlockObject(out);
      keyChild.fCompressed = true;
      keyChild.fValid = ret;
      return ret;
  }
  
  bool CExtKey::Derive(CExtKey& out, unsigned int nChild) const
  {
      out.nDepth = nDepth + 1;
      CKeyID id = key.GetPubKey().GetID();
      memcpy(&out.vchFingerprint[0], &id, 4);
      out.nChild = nChild;
      return key.Derive(out.key, out.vchChainCode, nChild, vchChainCode);
  }
  
  void CExtKey::SetMaster(const unsigned char* seed, unsigned int nSeedLen)
  {
      static const unsigned char hashkey[] = {'B', 'i', 't', 'c', 'o', 'i', 'n', ' ', 's', 'e', 'e', 'd'};
      unsigned char out[64];
      LockObject(out);
      CHMAC_SHA512(hashkey, sizeof(hashkey)).Write(seed, nSeedLen).Finalize(out);
      key.Set(&out[0], &out[32], true);
      memcpy(vchChainCode, &out[32], 32);
      UnlockObject(out);
      nDepth = 0;
      nChild = 0;
      memset(vchFingerprint, 0, sizeof(vchFingerprint));
  }
  
  CExtPubKey CExtKey::Neuter() const
  {
      CExtPubKey ret;
      ret.nDepth = nDepth;
      memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
      ret.nChild = nChild;
      ret.pubkey = key.GetPubKey();
      memcpy(&ret.vchChainCode[0], &vchChainCode[0], 32);
      return ret;
  }
  
  void CExtKey::Encode(unsigned char code[74]) const
  {
      code[0] = nDepth;
      memcpy(code + 1, vchFingerprint, 4);
      code[5] = (nChild >> 24) & 0xFF;
      code[6] = (nChild >> 16) & 0xFF;
      code[7] = (nChild >> 8) & 0xFF;
      code[8] = (nChild >> 0) & 0xFF;
      memcpy(code + 9, vchChainCode, 32);
      code[41] = 0;
      assert(key.size() == 32);
      memcpy(code + 42, key.begin(), 32);
  }
  
  void CExtKey::Decode(const unsigned char code[74])
  {
      nDepth = code[0];
      memcpy(vchFingerprint, code + 1, 4);
      nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
      memcpy(vchChainCode, code + 9, 32);
      key.Set(code + 42, code + 74, true);
  }
  
  bool ECC_InitSanityCheck()
  {
  #if !defined(USE_SECP256K1)
      if (!CECKey::SanityCheck()) {
          return false;
      }
  #endif
      CKey key;
      key.MakeNewKey(true);
      CPubKey pubkey = key.GetPubKey();
      return key.VerifyPubKey(pubkey);
  }
  