func (s *loaderServer) CreateWallet(ctx context.Context, req *pb.CreateWalletRequest) (
	*pb.CreateWalletResponse, error) {

	defer func() {
		zero.Bytes(req.PrivatePassphrase)
		zero.Bytes(req.Seed)
	}()

	// Use an insecure public passphrase when the request's is empty.
	pubPassphrase := req.PublicPassphrase
	if len(pubPassphrase) == 0 {
		pubPassphrase = []byte(wallet.InsecurePubPassphrase)
	}

	wallet, err := s.loader.CreateNewWallet(pubPassphrase, req.PrivatePassphrase, req.Seed)
	if err != nil {
		return nil, translateError(err)
	}

	s.mu.Lock()
	if s.rpcClient != nil {
		wallet.SynchronizeRPC(s.rpcClient)
	}
	s.mu.Unlock()

	return &pb.CreateWalletResponse{}, nil
}

func (s *walletServer) ImportPrivateKey(ctx context.Context, req *pb.ImportPrivateKeyRequest) (
	*pb.ImportPrivateKeyResponse, error) {

	defer zero.Bytes(req.Passphrase)

	wif, err := btcutil.DecodeWIF(req.PrivateKeyWif)
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Invalid WIF-encoded private key: %v", err)
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err = s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	// At the moment, only the special-cased import account can be used to
	// import keys.
	if req.Account != waddrmgr.ImportedAddrAccount {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Only the imported account accepts private key imports")
	}

	_, err = s.wallet.ImportPrivateKey(wif, nil, req.Rescan)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.ImportPrivateKeyResponse{}, nil
}

func (s *walletServer) ChangePassphrase(ctx context.Context, req *pb.ChangePassphraseRequest) (
	*pb.ChangePassphraseResponse, error) {

	defer func() {
		zero.Bytes(req.OldPassphrase)
		zero.Bytes(req.NewPassphrase)
	}()

	err := s.wallet.Manager.ChangePassphrase(req.OldPassphrase, req.NewPassphrase,
		req.Key != pb.ChangePassphraseRequest_PUBLIC, &waddrmgr.DefaultScryptOptions)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.ChangePassphraseResponse{}, nil
}

// lock zeroes the associated clear text private key.
func (a *scriptAddress) lock() {
	// Zero and nil the clear text script associated with this address.
	a.scriptMutex.Lock()
	zero.Bytes(a.scriptCT)
	a.scriptCT = nil
	a.scriptMutex.Unlock()
}

func (s *walletServer) NextAccount(ctx context.Context, req *pb.NextAccountRequest) (
	*pb.NextAccountResponse, error) {

	defer zero.Bytes(req.Passphrase)

	if req.AccountName == "" {
		return nil, grpc.Errorf(codes.InvalidArgument, "account name may not be empty")
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err := s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	account, err := s.wallet.NextAccount(req.AccountName)
	if err != nil {
		return nil, translateError(err)
	}

	return &pb.NextAccountResponse{AccountNumber: account}, nil
}

// PrivKey returns the private key for the address.  It can fail if the address
// manager is watching-only or locked, or the address does not have any keys.
//
// This is part of the ManagedPubKeyAddress interface implementation.
func (a *managedAddress) PrivKey() (*btcec.PrivateKey, error) {
	// No private keys are available for a watching-only address manager.
	if a.manager.watchingOnly {
		return nil, managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	a.manager.mtx.Lock()
	defer a.manager.mtx.Unlock()

	// Account manager must be unlocked to decrypt the private key.
	if a.manager.locked {
		return nil, managerError(ErrLocked, errLocked, nil)
	}

	// Decrypt the key as needed.  Also, make sure it's a copy since the
	// private key stored in memory can be cleared at any time.  Otherwise
	// the returned private key could be invalidated from under the caller.
	privKeyCopy, err := a.unlock(a.manager.cryptoKeyPriv)
	if err != nil {
		return nil, err
	}

	privKey, _ := btcec.PrivKeyFromBytes(btcec.S256(), privKeyCopy)
	zero.Bytes(privKeyCopy)
	return privKey, nil
}

func (s *loaderServer) StartBtcdRpc(ctx context.Context, req *pb.StartBtcdRpcRequest) (
	*pb.StartBtcdRpcResponse, error) {

	defer zero.Bytes(req.Password)

	defer s.mu.Unlock()
	s.mu.Lock()

	if s.rpcClient != nil {
		return nil, grpc.Errorf(codes.FailedPrecondition, "RPC client already created")
	}

	networkAddress, err := cfgutil.NormalizeAddress(req.NetworkAddress,
		s.activeNet.RPCClientPort)
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Network address is ill-formed: %v", err)
	}

	// Error if the wallet is already syncing with the network.
	wallet, walletLoaded := s.loader.LoadedWallet()
	if walletLoaded && wallet.SynchronizingToNetwork() {
		return nil, grpc.Errorf(codes.FailedPrecondition,
			"wallet is loaded and already synchronizing")
	}

	rpcClient, err := chain.NewRPCClient(s.activeNet.Params, networkAddress, req.Username,
		string(req.Password), req.Certificate, len(req.Certificate) == 0, 1)
	if err != nil {
		return nil, translateError(err)
	}

	err = rpcClient.Start()
	if err != nil {
		if err == btcrpcclient.ErrInvalidAuth {
			return nil, grpc.Errorf(codes.InvalidArgument,
				"Invalid RPC credentials: %v", err)
		} else {
			return nil, grpc.Errorf(codes.NotFound,
				"Connection to RPC server failed: %v", err)
		}
	}

	s.rpcClient = rpcClient

	if walletLoaded {
		wallet.SynchronizeRPC(rpcClient)
	}

	return &pb.StartBtcdRpcResponse{}, nil
}

// decryptExtendedKey uses Manager.Decrypt() to decrypt the encrypted byte slice and return
// an extended (public or private) key representing it.
//
// This method must be called with the Pool's manager unlocked.
func (p *Pool) decryptExtendedKey(keyType waddrmgr.CryptoKeyType, encrypted []byte) (*hdkeychain.ExtendedKey, error) {
	decrypted, err := p.manager.Decrypt(keyType, encrypted)
	if err != nil {
		str := fmt.Sprintf("cannot decrypt key %v", encrypted)
		return nil, newError(ErrCrypto, str, err)
	}
	result, err := hdkeychain.NewKeyFromString(string(decrypted))
	zero.Bytes(decrypted)
	if err != nil {
		str := fmt.Sprintf("cannot get key from string %v", decrypted)
		return nil, newError(ErrKeyChain, str, err)
	}
	return result, nil
}

// BUGS:
// - InputIndexes request field is ignored.
func (s *walletServer) SignTransaction(ctx context.Context, req *pb.SignTransactionRequest) (
	*pb.SignTransactionResponse, error) {

	defer zero.Bytes(req.Passphrase)

	var tx wire.MsgTx
	err := tx.Deserialize(bytes.NewReader(req.SerializedTransaction))
	if err != nil {
		return nil, grpc.Errorf(codes.InvalidArgument,
			"Bytes do not represent a valid raw transaction: %v", err)
	}

	lock := make(chan time.Time, 1)
	defer func() {
		lock <- time.Time{} // send matters, not the value
	}()
	err = s.wallet.Unlock(req.Passphrase, lock)
	if err != nil {
		return nil, translateError(err)
	}

	invalidSigs, err := s.wallet.SignTransaction(&tx, txscript.SigHashAll, nil, nil, nil)
	if err != nil {
		return nil, translateError(err)
	}

	invalidInputIndexes := make([]uint32, len(invalidSigs))
	for i, e := range invalidSigs {
		invalidInputIndexes[i] = e.InputIndex
	}

	var serializedTransaction bytes.Buffer
	serializedTransaction.Grow(tx.SerializeSize())
	err = tx.Serialize(&serializedTransaction)
	if err != nil {
		return nil, translateError(err)
	}

	resp := &pb.SignTransactionResponse{
		Transaction:          serializedTransaction.Bytes(),
		UnsignedInputIndexes: invalidInputIndexes,
	}
	return resp, nil
}

// deriveKey fills out the Key field.
func (sk *SecretKey) deriveKey(password *[]byte) error {
	key, err := scrypt.Key(*password, sk.Parameters.Salt[:],
		sk.Parameters.N,
		sk.Parameters.R,
		sk.Parameters.P,
		len(sk.Key))
	if err != nil {
		return err
	}
	copy(sk.Key[:], key)
	zero.Bytes(key)

	// I'm not a fan of forced garbage collections, but scrypt allocates a
	// ton of memory and calling it back to back without a GC cycle in
	// between means you end up needing twice the amount of memory.  For
	// example, if your scrypt parameters are such that you require 1GB and
	// you call it twice in a row, without this you end up allocating 2GB
	// since the first GB probably hasn't been released yet.
	debug.FreeOSMemory()

	return nil
}