text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2015 The Bitcoin Core developers
  // Copyright (c) 2015-2019 The Bitcoin Unlimited developers
  // Copyright (c) 2017 The Zcash developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef BITCOIN_KEY_H
  #define BITCOIN_KEY_H
  
  #include "pubkey.h"
  #include "serialize.h"
  #include "support/allocators/secure.h"
  #include "uint256.h"
  
  #include <stdexcept>
  #include <vector>
  
  extern const uint32_t BIP32_HARDENED_KEY_LIMIT;
  
  
  /**
   * secure_allocator is defined in allocators.h
   * CPrivKey is a serialized private key, with all parameters included (PRIVATE_KEY_SIZE bytes)
   */
  typedef std::vector<unsigned char, secure_allocator<unsigned char> > CPrivKey;
  
  /** An encapsulated secp256k1 private key. */
  class CKey
  {
  public:
      /**
       * secp256k1:
       */
      static const unsigned int PRIVATE_KEY_SIZE = 279;
      static const unsigned int COMPRESSED_PRIVATE_KEY_SIZE = 214;
      /**
       * see www.keylength.com
       * script supports up to 75 for single byte push
       */
      static_assert(PRIVATE_KEY_SIZE >= COMPRESSED_PRIVATE_KEY_SIZE,
          "COMPRESSED_PRIVATE_KEY_SIZE is larger than PRIVATE_KEY_SIZE");
  
  
  private:
      //! Whether this private key is valid. We check for correctness when modifying the key
      //! data, so fValid should always correspond to the actual state.
      bool fValid;
  
      //! Whether the public key corresponding to this private key is (to be) compressed.
      bool fCompressed;
  
      //! The actual byte data
      unsigned char vch[32];
  
      //! Check whether the 32-byte array pointed to be vch is valid keydata.
      bool static Check(const unsigned char *vch);
  
  public:
      //! Construct an invalid private key.
      CKey() : fValid(false), fCompressed(false) { LockObject(vch); }
      //! Copy constructor. This is necessary because of memlocking.
      CKey(const CKey &secret) : fValid(secret.fValid), fCompressed(secret.fCompressed)
      {
          LockObject(vch);
          memcpy(vch, secret.vch, sizeof(vch));
      }
      CKey &operator=(const CKey &secret)
      {
          fValid = secret.fValid;
          fCompressed = secret.fCompressed;
          LockObject(vch);
          memcpy(vch, secret.vch, sizeof(vch));
          return *this;
      }
  
      //! Destructor (again necessary because of memlocking).
      ~CKey() { UnlockObject(vch); }
      friend bool operator==(const CKey &a, const CKey &b)
      {
          return a.fCompressed == b.fCompressed && a.size() == b.size() && memcmp(&a.vch[0], &b.vch[0], a.size()) == 0;
      }
  
      //! Initialize using begin and end iterators to byte data.
      template <typename T>
      void Set(const T pbegin, const T pend, bool fCompressedIn)
      {
          if (pend - pbegin != 32)
          {
              fValid = false;
              return;
          }
          if (Check(&pbegin[0]))
          {
              memcpy(vch, (unsigned char *)&pbegin[0], 32);
              fValid = true;
              fCompressed = fCompressedIn;
          }
          else
          {
              fValid = false;
          }
      }
  
      //! Simple read-only vector-like interface.
      unsigned int size() const { return (fValid ? 32 : 0); }
      const unsigned char *begin() const { return vch; }
      const unsigned char *end() const { return vch + size(); }
      //! Check whether this private key is valid.
      bool IsValid() const { return fValid; }
      //! Check whether the public key corresponding to this private key is (to be) compressed.
      bool IsCompressed() const { return fCompressed; }
      //! Initialize from a CPrivKey (serialized OpenSSL private key data).
      bool SetPrivKey(const CPrivKey &vchPrivKey, bool fCompressed);
  
      //! Generate a new private key using a cryptographic PRNG.
      void MakeNewKey(bool fCompressed);
  
      /**
       * Convert the private key to a CPrivKey (serialized OpenSSL private key data).
       * This is expensive.
       */
      CPrivKey GetPrivKey() const;
  
      /**
       * Compute the public key from a private key.
       * This is expensive.
       */
      CPubKey GetPubKey() const;
  
      /**
       * Create a DER-serialized ECDSA signature.
       * The test_case parameter tweaks the deterministic nonce.
       */
      bool SignECDSA(const uint256 &hash, std::vector<unsigned char> &vchSig, uint32_t test_case = 0) const;
  
      /**
       * Create a Schnorr signature.
       * The test_case parameter tweaks the deterministic nonce.
       */
      bool SignSchnorr(const uint256 &hash, std::vector<uint8_t> &vchSig, uint32_t test_case = 0) const;
  
      /**
       * 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,
       *                  add 0x04 for compressed keys.
       */
      bool SignCompact(const uint256 &hash, std::vector<unsigned char> &vchSig) const;
  
      //! Derive BIP32 child key.
      bool Derive(CKey &keyChild, ChainCode &ccChild, unsigned int nChild, const ChainCode &cc) const;
  
      /**
       * Verify thoroughly whether a private key and a public key match.
       * This is done using a different mechanism than just regenerating it.
       * (An ECDSA signature is created then verified.)
       */
      bool VerifyPubKey(const CPubKey &vchPubKey) const;
  
      //! Load private key and check that public key matches.
      bool Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck);
  
      //! Check whether an element of a signature (r or s) is valid.
      static bool CheckSignatureElement(const unsigned char *vch, int len, bool half);
  };
  
  struct CExtKey
  {
      unsigned char nDepth;
      unsigned char vchFingerprint[4];
      unsigned int nChild;
      ChainCode chaincode;
      CKey key;
  
      friend bool operator==(const CExtKey &a, const CExtKey &b)
      {
          return a.nDepth == b.nDepth && memcmp(&a.vchFingerprint[0], &b.vchFingerprint[0], 4) == 0 &&
                 a.nChild == b.nChild && a.chaincode == b.chaincode && a.key == b.key;
      }
  
      void Encode(unsigned char code[BIP32_EXTKEY_SIZE]) const;
      void Decode(const unsigned char code[BIP32_EXTKEY_SIZE]);
      bool Derive(CExtKey &out, unsigned int nChild) const;
      CExtPubKey Neuter() const;
      void SetMaster(const unsigned char *seed, unsigned int nSeedLen);
      template <typename Stream>
      void Serialize(Stream &s) const
      {
          unsigned int len = BIP32_EXTKEY_SIZE;
          ::WriteCompactSize(s, len);
          unsigned char code[BIP32_EXTKEY_SIZE];
          Encode(code);
          s.write((const char *)&code[0], len);
      }
      template <typename Stream>
      void Unserialize(Stream &s)
      {
          unsigned int len = ::ReadCompactSize(s);
          if (len != BIP32_EXTKEY_SIZE)
          {
              throw std::runtime_error("Invalid extended key size\n");
          }
          unsigned char code[BIP32_EXTKEY_SIZE];
          s.read((char *)&code[0], len);
          Decode(code);
      }
  };
  
  /** Initialize the elliptic curve support. May not be called twice without calling ECC_Stop first. */
  void ECC_Start(void);
  
  /** Deinitialize the elliptic curve support. No-op if ECC_Start wasn't called first. */
  void ECC_Stop(void);
  
  /** Check that required EC support is available at runtime. */
  bool ECC_InitSanityCheck(void);
  
  /** Derive a BIP-0032 heirarchial deterministic wallet key */
  int Hd32DeriveChildKey(CKey key, int externalChainCounter, CKey &secret, std::string *keypath);
  
  /** Derive a BIP-0044 heirarchial deterministic wallet key */
  int Hd44DeriveChildKey(unsigned char *secretSeed,
      unsigned int secretSeedLen,
      unsigned int purpose,
      unsigned int coinType,
      unsigned int account,
      bool change,
      unsigned int index,
      CKey &secret,
      std::string *keypath);
  
  
  #endif // BITCOIN_KEY_H
  