text: // Copyright (c) 2009-2012 The Bitcoin developers
  // Distributed under the MIT/X11 software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <openssl/bn.h>
  #include <openssl/ecdsa.h>
  #include <openssl/rand.h>
  #include <openssl/obj_mac.h>
  
  #include "key.h"
  
  
  // anonymous namespace with local implementation code (OpenSSL interaction)
  namespace {
  
  // 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 non-zero, 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;
  }
  
  // RAII Wrapper around OpenSSL's EC_KEY
  class CECKey {
  private:
      EC_KEY *pkey;
  
  public:
      CECKey() {
          pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
          assert(pkey != NULL);
      }
  
      ~CECKey() {
          EC_KEY_free(pkey);
      }
  
      void GetSecretBytes(unsigned char vch[32]) const {
          const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
          assert(bn);
          int nBytes = BN_num_bytes(bn);
          int n=BN_bn2bin(bn,&vch[32 - nBytes]);
          assert(n == nBytes);
          memset(vch, 0, 32 - nBytes);
      }
  
      void SetSecretBytes(const unsigned char vch[32]) {
          bool ret;
          BIGNUM bn;
          BN_init(&bn);
          ret = BN_bin2bn(vch, 32, &bn);
          assert(ret);
          ret = EC_KEY_regenerate_key(pkey, &bn);
          assert(ret);
          BN_clear_free(&bn);
      }
  
      void GetPrivKey(CPrivKey &privkey, bool fCompressed) {
          EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
          int nSize = i2d_ECPrivateKey(pkey, NULL);
          assert(nSize);
          privkey.resize(nSize);
          unsigned char* pbegin = &privkey[0];
          int nSize2 = i2d_ECPrivateKey(pkey, &pbegin);
          assert(nSize == nSize2);
      }
  
      bool SetPrivKey(const CPrivKey &privkey, bool fSkipCheck=false) {
          const unsigned char* pbegin = &privkey[0];
          if (d2i_ECPrivateKey(&pkey, &pbegin, privkey.size())) {
              if(fSkipCheck)
                  return true;
  
              // d2i_ECPrivateKey returns true if parsing succeeds.
              // This doesn't necessarily mean the key is valid.
              if (EC_KEY_check_key(pkey))
                  return true;
          }
          return false;
      }
  
      void GetPubKey(CPubKey &pubkey, bool fCompressed) {
          EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
          int nSize = i2o_ECPublicKey(pkey, NULL);
          assert(nSize);
          assert(nSize <= 65);
          unsigned char c[65];
          unsigned char *pbegin = c;
          int nSize2 = i2o_ECPublicKey(pkey, &pbegin);
          assert(nSize == nSize2);
          pubkey.Set(&c[0], &c[nSize]);
      }
  
      bool SetPubKey(const CPubKey &pubkey) {
          const unsigned char* pbegin = pubkey.begin();
          return o2i_ECPublicKey(&pkey, &pbegin, pubkey.size());
      }
  
      bool Sign(const uint256 &hash, std::vector<unsigned char>& vchSig) {
          vchSig.clear();
          ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
          if (sig == NULL)
              return false;
          BN_CTX *ctx = BN_CTX_new();
          BN_CTX_start(ctx);
          const EC_GROUP *group = EC_KEY_get0_group(pkey);
          BIGNUM *order = BN_CTX_get(ctx);
          BIGNUM *halforder = BN_CTX_get(ctx);
          EC_GROUP_get_order(group, order, ctx);
          BN_rshift1(halforder, order);
          if (BN_cmp(sig->s, halforder) > 0) {
              // enforce low S values, by negating the value (modulo the order) if above order/2.
              BN_sub(sig->s, order, sig->s);
          }
          BN_CTX_end(ctx);
          BN_CTX_free(ctx);
          unsigned int nSize = ECDSA_size(pkey);
          vchSig.resize(nSize); // Make sure it is big enough
          unsigned char *pos = &vchSig[0];
          nSize = i2d_ECDSA_SIG(sig, &pos);
          ECDSA_SIG_free(sig);
          vchSig.resize(nSize); // Shrink to fit actual size
          return true;
      }
  
      bool Verify(const 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 SignCompact(const uint256 &hash, unsigned char *p64, int &rec) {
          bool fOk = false;
          ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
          if (sig==NULL)
              return false;
          memset(p64, 0, 64);
          int nBitsR = BN_num_bits(sig->r);
          int nBitsS = BN_num_bits(sig->s);
          if (nBitsR <= 256 && nBitsS <= 256) {
              CPubKey pubkey;
              GetPubKey(pubkey, true);
              for (int i=0; i<4; i++) {
                  CECKey keyRec;
                  if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1) {
                      CPubKey pubkeyRec;
                      keyRec.GetPubKey(pubkeyRec, true);
                      if (pubkeyRec == pubkey) {
                          rec = i;
                          fOk = true;
                          break;
                      }
                  }
              }
              assert(fOk);
              BN_bn2bin(sig->r,&p64[32-(nBitsR+7)/8]);
              BN_bn2bin(sig->s,&p64[64-(nBitsS+7)/8]);
          }
          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 Recover(const uint256 &hash, const unsigned char *p64, int rec)
      {
          if (rec<0 || rec>=3)
              return false;
          ECDSA_SIG *sig = ECDSA_SIG_new();
          BN_bin2bn(&p64[0],  32, sig->r);
          BN_bin2bn(&p64[32], 32, sig->s);
          bool ret = ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), rec, 0) == 1;
          ECDSA_SIG_free(sig);
          return ret;
      }
  
      static bool TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32])
      {
          bool ret = true;
          BN_CTX *ctx = BN_CTX_new();
          BN_CTX_start(ctx);
          BIGNUM *bnSecret = BN_CTX_get(ctx);
          BIGNUM *bnTweak = BN_CTX_get(ctx);
          BIGNUM *bnOrder = BN_CTX_get(ctx);
          EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_secp256k1);
          EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
          BN_bin2bn(vchTweak, 32, bnTweak);
          if (BN_cmp(bnTweak, bnOrder) >= 0)
              ret = false; // extremely unlikely
          BN_bin2bn(vchSecretIn, 32, bnSecret);
          BN_add(bnSecret, bnSecret, bnTweak);
          BN_nnmod(bnSecret, bnSecret, bnOrder, ctx);
          if (BN_is_zero(bnSecret))
              ret = false; // ridiculously unlikely
          int nBits = BN_num_bits(bnSecret);
          memset(vchSecretOut, 0, 32);
          BN_bn2bin(bnSecret, &vchSecretOut[32-(nBits+7)/8]);
          EC_GROUP_free(group);
          BN_CTX_end(ctx);
          BN_CTX_free(ctx);
          return ret;
      }
  
      bool TweakPublic(const unsigned char vchTweak[32]) {
          bool ret = true;
          BN_CTX *ctx = BN_CTX_new();
          BN_CTX_start(ctx);
          BIGNUM *bnTweak = BN_CTX_get(ctx);
          BIGNUM *bnOrder = BN_CTX_get(ctx);
          BIGNUM *bnOne = BN_CTX_get(ctx);
          const EC_GROUP *group = EC_KEY_get0_group(pkey);
          EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
          BN_bin2bn(vchTweak, 32, bnTweak);
          if (BN_cmp(bnTweak, bnOrder) >= 0)
              ret = false; // extremely unlikely
          EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group);
          BN_one(bnOne);
          EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx);
          if (EC_POINT_is_at_infinity(group, point))
              ret = false; // ridiculously unlikely
          EC_KEY_set_public_key(pkey, point);
          EC_POINT_free(point);
          BN_CTX_end(ctx);
          BN_CTX_free(ctx);
          return ret;
      }
  };
  
  int CompareBigEndian(const unsigned char *c1, size_t c1len, const unsigned char *c2, size_t c2len) {
      while (c1len > c2len) {
          if (*c1)
              return 1;
          c1++;
          c1len--;
      }
      while (c2len > c1len) {
          if (*c2)
              return -1;
          c2++;
          c2len--;
      }
      while (c1len > 0) {
          if (*c1 > *c2)
              return 1;
          if (*c2 > *c1)
              return -1;
          c1++;
          c2++;
          c1len--;
      }
      return 0;
  }
  
  // Order of secp256k1's generator minus 1.
  const unsigned char vchMaxModOrder[32] = {
      0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
      0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
      0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
      0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
  };
  
  // Half of the order of secp256k1's generator minus 1.
  const unsigned char vchMaxModHalfOrder[32] = {
      0x7F,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
      0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
      0x5D,0x57,0x6E,0x73,0x57,0xA4,0x50,0x1D,
      0xDF,0xE9,0x2F,0x46,0x68,0x1B,0x20,0xA0
  };
  
  const unsigned char vchZero[0] = {};
  
  }; // end of anonymous namespace
  
  bool CKey::Check(const unsigned char *vch) {
      // Do not convert to OpenSSL's data structures for range-checking keys,
      // it's easy enough to do directly.
      static const unsigned char vchMax[32] = {
          0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
          0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
          0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
          0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
      };
      bool fIsZero = true;
      for (int i=0; i<32 && fIsZero; i++)
          if (vch[i] != 0)
              fIsZero = false;
      if (fIsZero)
          return false;
      for (int i=0; i<32; i++) {
          if (vch[i] < vchMax[i])
              return true;
          if (vch[i] > vchMax[i])
              return false;
      }
      return true;
  }
  
  bool CKey::CheckSignatureElement(const unsigned char *vch, int len, bool half) {
      return CompareBigEndian(vch, len, vchZero, 0) > 0 &&
             CompareBigEndian(vch, len, half ? vchMaxModHalfOrder : vchMaxModOrder, 32) <= 0;
  }
  
  bool CKey::ReserealizeSignature(std::vector<unsigned char>& vchSig) {
      unsigned char *pos;
  
      if (vchSig.empty())
          return false;
  
      pos = &vchSig[0];
      ECDSA_SIG *sig = d2i_ECDSA_SIG(NULL, (const unsigned char **)&pos, vchSig.size());
      if (sig == NULL)
          return false;
  
      bool ret = false;
      int nSize = i2d_ECDSA_SIG(sig, NULL);
      if (nSize > 0) {
          vchSig.resize(nSize); // grow or shrink as needed
  
          pos = &vchSig[0];
          i2d_ECDSA_SIG(sig, &pos);
  
          ret = true;
      }
  
      ECDSA_SIG_free(sig);
      return ret;
  }
  
  void CKey::MakeNewKey(bool fCompressedIn) {
      do {
          RAND_bytes(vch, sizeof(vch));
      } while (!Check(vch));
      fValid = true;
      fCompressed = fCompressedIn;
  }
  
  bool CKey::SetPrivKey(const CPrivKey &privkey, bool fCompressedIn) {
      CECKey key;
      if (!key.SetPrivKey(privkey))
          return false;
      key.GetSecretBytes(vch);
      fCompressed = fCompressedIn;
      fValid = true;
      return true;
  }
  
  CPrivKey CKey::GetPrivKey() const {
      assert(fValid);
      CECKey key;
      key.SetSecretBytes(vch);
      CPrivKey privkey;
      key.GetPrivKey(privkey, fCompressed);
      return privkey;
  }
  
  CPubKey CKey::GetPubKey() const {
      assert(fValid);
      CECKey key;
      key.SetSecretBytes(vch);
      CPubKey pubkey;
      key.GetPubKey(pubkey, fCompressed);
      return pubkey;
  }
  
  bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
      if (!fValid)
          return false;
      CECKey key;
      key.SetSecretBytes(vch);
      return key.Sign(hash, vchSig);
  }
  
  bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
      if (!fValid)
          return false;
      CECKey key;
      key.SetSecretBytes(vch);
      vchSig.resize(65);
      int rec = -1;
      if (!key.SignCompact(hash, &vchSig[1], rec))
          return false;
      assert(rec != -1);
      vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
      return true;
  }
  
  bool CKey::Load(CPrivKey &privkey, CPubKey &vchPubKey, bool fSkipCheck=false) {
      CECKey key;
      if (!key.SetPrivKey(privkey, fSkipCheck))
          return false;
  
      key.GetSecretBytes(vch);
      fCompressed = vchPubKey.IsCompressed();
      fValid = true;
  
      if (fSkipCheck)
          return true;
  
      if (GetPubKey() != vchPubKey)
          return false;
  
      return true;
  }
  
  bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
      if (!IsValid())
          return false;
      CECKey key;
      if (!key.SetPubKey(*this))
          return false;
      if (!key.Verify(hash, vchSig))
          return false;
      return true;
  }
  
  bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
      if (vchSig.size() != 65)
          return false;
      CECKey key;
      if (!key.Recover(hash, &vchSig[1], (vchSig[0] - 27) & ~4))
          return false;
      key.GetPubKey(*this, (vchSig[0] - 27) & 4);
      return true;
  }
  
  bool CPubKey::VerifyCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
      if (!IsValid())
          return false;
      if (vchSig.size() != 65)
          return false;
      CECKey key;
      if (!key.Recover(hash, &vchSig[1], (vchSig[0] - 27) & ~4))
          return false;
      CPubKey pubkeyRec;
      key.GetPubKey(pubkeyRec, IsCompressed());
      if (*this != pubkeyRec)
          return false;
      return true;
  }
  
  bool CPubKey::IsFullyValid() const {
      if (!IsValid())
          return false;
      CECKey key;
      if (!key.SetPubKey(*this))
          return false;
      return true;
  }
  
  bool CPubKey::Decompress() {
      if (!IsValid())
          return false;
      CECKey key;
      if (!key.SetPubKey(*this))
          return false;
      key.GetPubKey(*this, false);
      return true;
  }
  
  void static BIP32Hash(const unsigned char chainCode[32], unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64]) {
      unsigned char num[4];
      num[0] = (nChild >> 24) & 0xFF;
      num[1] = (nChild >> 16) & 0xFF;
      num[2] = (nChild >>  8) & 0xFF;
      num[3] = (nChild >>  0) & 0xFF;
      HMAC_SHA512_CTX ctx;
      HMAC_SHA512_Init(&ctx, chainCode, 32);
      HMAC_SHA512_Update(&ctx, &header, 1);
      HMAC_SHA512_Update(&ctx, data, 32);
      HMAC_SHA512_Update(&ctx, num, 4);
      HMAC_SHA512_Final(output, &ctx);
  }
  
  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);
      bool ret = CECKey::TweakSecret((unsigned char*)keyChild.begin(), begin(), out);
      UnlockObject(out);
      keyChild.fCompressed = true;
      keyChild.fValid = ret;
      return ret;
  }
  
  bool CPubKey::Derive(CPubKey& pubkeyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const {
      assert(IsValid());
      assert((nChild >> 31) == 0);
      assert(begin() + 33 == end());
      unsigned char out[64];
      BIP32Hash(cc, nChild, *begin(), begin()+1, out);
      memcpy(ccChild, out+32, 32);
      CECKey key;
      bool ret = key.SetPubKey(*this);
      ret &= key.TweakPublic(out);
      key.GetPubKey(pubkeyChild, true);
      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 char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
      HMAC_SHA512_CTX ctx;
      HMAC_SHA512_Init(&ctx, hashkey, sizeof(hashkey));
      HMAC_SHA512_Update(&ctx, seed, nSeedLen);
      unsigned char out[64];
      LockObject(out);
      HMAC_SHA512_Final(out, &ctx);
      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);
  }
  
  void CExtPubKey::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);
      assert(pubkey.size() == 33);
      memcpy(code+41, pubkey.begin(), 33);
  }
  
  void CExtPubKey::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);
      pubkey.Set(code+41, code+74);
  }
  
  bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const {
      out.nDepth = nDepth + 1;
      CKeyID id = pubkey.GetID();
      memcpy(&out.vchFingerprint[0], &id, 4);
      out.nChild = nChild;
      return pubkey.Derive(out.pubkey, out.vchChainCode, nChild, vchChainCode);
  }
  
  bool ECC_InitSanityCheck() {
      EC_KEY *pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
      if(pkey == NULL)
          return false;
      EC_KEY_free(pkey);
  
      // TODO Is there more EC functionality that could be missing?
      return true;
  }
  