protected override async Task <ECDSASignature> SignExternallyAsync(byte[] bytes)
        {
            // Specify the path to unmanaged PKCS#11 library provided by the cryptographic device vendor
            string pkcs11LibraryPath = @"/opt/cloudhsm/lib/libcloudhsm_pkcs11_standard.so";

            // Create factories used by Pkcs11Interop library
            Net.Pkcs11Interop.HighLevelAPI.Pkcs11InteropFactories factories = new Net.Pkcs11Interop.HighLevelAPI.Pkcs11InteropFactories();

            // Load unmanaged PKCS#11 library
            using (Net.Pkcs11Interop.HighLevelAPI.IPkcs11Library pkcs11Library = factories.Pkcs11LibraryFactory.LoadPkcs11Library(factories, pkcs11LibraryPath, AppType.MultiThreaded))
            {
                // Show general information about loaded library
                Net.Pkcs11Interop.HighLevelAPI.ILibraryInfo libraryInfo = pkcs11Library.GetInfo();

                Console.WriteLine("Library");
                Console.WriteLine("  Manufacturer:       " + libraryInfo.ManufacturerId);
                Console.WriteLine("  Description:        " + libraryInfo.LibraryDescription);
                Console.WriteLine("  Version:            " + libraryInfo.LibraryVersion);

                // Get list of all available slots
                foreach (Net.Pkcs11Interop.HighLevelAPI.ISlot slot in pkcs11Library.GetSlotList(SlotsType.WithOrWithoutTokenPresent))
                {
                    // Show basic information about slot
                    Net.Pkcs11Interop.HighLevelAPI.ISlotInfo slotInfo = slot.GetSlotInfo();

                    Console.WriteLine();
                    Console.WriteLine("Slot");
                    Console.WriteLine("  Manufacturer:       " + slotInfo.ManufacturerId);
                    Console.WriteLine("  Description:        " + slotInfo.SlotDescription);
                    Console.WriteLine("  Token present:      " + slotInfo.SlotFlags.TokenPresent);

                    if (slotInfo.SlotFlags.TokenPresent)
                    {
                        // Show basic information about token present in the slot
                        Net.Pkcs11Interop.HighLevelAPI.ITokenInfo tokenInfo = slot.GetTokenInfo();

                        Console.WriteLine("Token");
                        Console.WriteLine("  Manufacturer:       " + tokenInfo.ManufacturerId);
                        Console.WriteLine("  Model:              " + tokenInfo.Model);
                        Console.WriteLine("  Serial number:      " + tokenInfo.SerialNumber);
                        Console.WriteLine("  Label:              " + tokenInfo.Label);

                        // Show list of mechanisms (algorithms) supported by the token
                        Console.WriteLine("Supported mechanisms: ");
                        foreach (CKM mechanism in slot.GetMechanismList())
                        {
                            Console.WriteLine("  " + mechanism);
                        }
                    }

                    using (Net.Pkcs11Interop.HighLevelAPI.ISession session = slot.OpenSession(SessionType.ReadWrite))
                    {
                        session.Login(CKU.CKU_USER, pkcsUser);

                        // Specify signing mechanism
                        Net.Pkcs11Interop.HighLevelAPI.IMechanism mechanism = session.Factories.MechanismFactory.Create(CKM.CKM_ECDSA);

                        List <Net.Pkcs11Interop.HighLevelAPI.IObjectAttribute> publicKeyAttributes = new List <Net.Pkcs11Interop.HighLevelAPI.IObjectAttribute>();
                        publicKeyAttributes.Add(new Net.Pkcs11Interop.HighLevelAPI80.ObjectAttribute(CKA.CKA_LABEL, hsmKey));
                        publicKeyAttributes.Add(new Net.Pkcs11Interop.HighLevelAPI80.ObjectAttribute(CKA.CKA_SIGN, true));

                        Net.Pkcs11Interop.HighLevelAPI.IObjectHandle key = session.FindAllObjects(publicKeyAttributes).FirstOrDefault();


                        byte[] signature = session.Sign(mechanism, key, bytes);
                        Console.WriteLine("signature: " + BitConverter.ToString(signature));
                        session.Logout();

                        return(await Task.FromResult(ECDSASignatureFactory.FromComponents(signature).MakeCanonical()));
                    }
                }
            }
            return(null);
        }
        public async Task <string> WithdrawBtc(string withdrawHash, string recipient, decimal amount)
        {
            var coins        = new List <UTXO>();
            var coinsUsed    = new List <UTXO>();
            var estimatedFee = await client.GetFeeRateAsync(3);

            try
            {
                await locker.WaitAsync();

                while (coinsUsed.Sum(c => c.AsCoin().Amount.ToDecimal(MoneyUnit.BTC)) <= amount)
                {
                    var txOperations = await client.GetUTXOsAsync(TrackedSource.Create(pubKey.GetAddress(ScriptPubKeyType.Legacy, Network.Main)));

                    foreach (var op in txOperations.Confirmed.UTXOs)
                    {
                        if (!usedInputs.ContainsKey(op.TransactionHash.ToString() + op.Value.Satoshi.ToString()))
                        {
                            coins.Add(op);
                        }
                    }

                    coins.Sort(delegate(UTXO x, UTXO y)
                    {
                        return(-x.AsCoin().Amount.CompareTo(y.AsCoin().Amount));
                    });

                    foreach (var item in coins)
                    {
                        if (coinsUsed.Sum(c => c.AsCoin().Amount.ToDecimal(MoneyUnit.BTC)) <= amount)
                        {
                            coinsUsed.Add(item);
                            usedInputs.Add(item.TransactionHash.ToString() + item.Value.Satoshi.ToString(), item);
                        }
                        else
                        {
                            break;
                        }
                    }

                    if (coinsUsed.Sum(c => c.AsCoin().Amount.ToDecimal(MoneyUnit.BTC)) < amount)
                    {
                        await Task.Delay(5000);
                    }
                }

                TransactionBuilder   builder     = null;
                BitcoinPubKeyAddress destination = null;
                if (network == NetworkType.Testnet)
                {
                    builder     = Network.TestNet.CreateTransactionBuilder();
                    destination = new BitcoinPubKeyAddress(recipient, Network.TestNet);
                }
                else
                {
                    builder     = Network.Main.CreateTransactionBuilder();
                    destination = new BitcoinPubKeyAddress(recipient, Network.Main);
                }

                NBitcoin.Transaction tx = builder
                                          .AddCoins(coinsUsed.Select(c => c.AsCoin() /* .ScriptPubKey.ToBytes()*/))
                                          .Send(destination, Money.Coins(amount))
                                          .Send(TxNullDataTemplate.Instance.GenerateScriptPubKey(Encoding.UTF8.GetBytes(withdrawHash)), Money.Zero)
                                          .SetChange(pubKey.GetAddress(ScriptPubKeyType.Legacy, Network.Main))
                                          .SendEstimatedFees((await client.GetFeeRateAsync(3)).FeeRate)
                                          .BuildTransaction(sign: false);

                // Specify the path to unmanaged PKCS#11 library provided by the cryptographic device vendor
                string pkcs11LibraryPath = @"/opt/cloudhsm/lib/libcloudhsm_pkcs11_standard.so";

                // Create factories used by Pkcs11Interop library
                Net.Pkcs11Interop.HighLevelAPI.Pkcs11InteropFactories factories = new Net.Pkcs11Interop.HighLevelAPI.Pkcs11InteropFactories();

                // Load unmanaged PKCS#11 library
                using (Net.Pkcs11Interop.HighLevelAPI.IPkcs11Library pkcs11Library = factories.Pkcs11LibraryFactory.LoadPkcs11Library(factories, pkcs11LibraryPath, AppType.MultiThreaded))
                {
                    // Show general information about loaded library
                    Net.Pkcs11Interop.HighLevelAPI.ILibraryInfo libraryInfo = pkcs11Library.GetInfo();

                    Console.WriteLine("Library");
                    Console.WriteLine("  Manufacturer:       " + libraryInfo.ManufacturerId);
                    Console.WriteLine("  Description:        " + libraryInfo.LibraryDescription);
                    Console.WriteLine("  Version:            " + libraryInfo.LibraryVersion);

                    // Get list of all available slots
                    foreach (Net.Pkcs11Interop.HighLevelAPI.ISlot slot in pkcs11Library.GetSlotList(SlotsType.WithOrWithoutTokenPresent))
                    {
                        // Show basic information about slot
                        Net.Pkcs11Interop.HighLevelAPI.ISlotInfo slotInfo = slot.GetSlotInfo();

                        Console.WriteLine();
                        Console.WriteLine("Slot");
                        Console.WriteLine("  Manufacturer:       " + slotInfo.ManufacturerId);
                        Console.WriteLine("  Description:        " + slotInfo.SlotDescription);
                        Console.WriteLine("  Token present:      " + slotInfo.SlotFlags.TokenPresent);

                        if (slotInfo.SlotFlags.TokenPresent)
                        {
                            // Show basic information about token present in the slot
                            Net.Pkcs11Interop.HighLevelAPI.ITokenInfo tokenInfo = slot.GetTokenInfo();

                            Console.WriteLine("Token");
                            Console.WriteLine("  Manufacturer:       " + tokenInfo.ManufacturerId);
                            Console.WriteLine("  Model:              " + tokenInfo.Model);
                            Console.WriteLine("  Serial number:      " + tokenInfo.SerialNumber);
                            Console.WriteLine("  Label:              " + tokenInfo.Label);

                            // Show list of mechanisms (algorithms) supported by the token
                            Console.WriteLine("Supported mechanisms: ");
                            foreach (CKM mechanism in slot.GetMechanismList())
                            {
                                Console.WriteLine("  " + mechanism);
                            }
                        }

                        using (Net.Pkcs11Interop.HighLevelAPI.ISession session = slot.OpenSession(SessionType.ReadWrite))
                        {
                            session.Login(CKU.CKU_USER, pkcsUser);

                            // Specify signing mechanism
                            Net.Pkcs11Interop.HighLevelAPI.IMechanism mechanism = session.Factories.MechanismFactory.Create(CKM.CKM_ECDSA);

                            List <Net.Pkcs11Interop.HighLevelAPI.IObjectAttribute> publicKeyAttributes = new List <Net.Pkcs11Interop.HighLevelAPI.IObjectAttribute>();
                            publicKeyAttributes.Add(new Net.Pkcs11Interop.HighLevelAPI80.ObjectAttribute(CKA.CKA_LABEL, hsmKey));
                            publicKeyAttributes.Add(new Net.Pkcs11Interop.HighLevelAPI80.ObjectAttribute(CKA.CKA_SIGN, true));


                            Net.Pkcs11Interop.HighLevelAPI.IObjectHandle key = session.FindAllObjects(publicKeyAttributes).FirstOrDefault();

                            uint i = 0;
                            foreach (var c in tx.Inputs.AsIndexedInputs())
                            {
                                byte[] sourceData = c.GetSignatureHash(coinsUsed.First(cu => cu.Outpoint.Hash == c.PrevOut.Hash).AsCoin()).ToBytes();
                                Console.WriteLine("sourceData: " + tx.ToHex());

                                byte[] signature = session.Sign(mechanism, key, sourceData);
                                Console.WriteLine("signature: " + BitConverter.ToString(signature));
                                var canSig = ECDSASignatureFactory.FromComponents(signature).MakeCanonical();
                                var sig    = new NBitcoin.TransactionSignature(new NBitcoin.Crypto.ECDSASignature(new NBitcoin.BouncyCastle.Math.BigInteger(canSig.R.ToByteArray()), new NBitcoin.BouncyCastle.Math.BigInteger(canSig.S.ToByteArray())), SigHash.Single);
                                builder = builder.AddKnownSignature(pubKey, sig, c.PrevOut);
                                TransactionSignature sig2 = null;
                                if (builder.TrySignInput(tx, i, SigHash.Single, out sig2))
                                {
                                    Console.WriteLine("Input Signed");
                                    Console.WriteLine(BitConverter.ToString(sig2.ToBytes()));
                                }
                                else
                                {
                                    Console.WriteLine("Input Not Signed");
                                }

                                Console.WriteLine("tx: " + tx);
                                i++;

                                tx = builder.SignTransactionInPlace(tx);
                            }


                            Console.WriteLine("tx: " + tx);
                            TransactionPolicyError[] errors = null;
                            if (builder.Verify(tx, out errors))
                            {
                                var broadcastResult = await client.BroadcastAsync(tx);

                                broadcastResult.ToString();
                                Console.WriteLine("broadcast: " + tx.GetHash().ToString());
                                session.Logout();
                                return(tx.GetHash().ToString());
                            }
                            else
                            {
                                Console.WriteLine("Verify transaction failed");
                            }

                            if (errors != null)
                            {
                                foreach (var e in errors)
                                {
                                    Console.WriteLine(e.ToString());
                                }
                            }

                            session.Logout();
                        }
                    }
                }

                return(null);
            }
            catch (Exception e)
            {
                Log.Error("Failed to send BTC Withdraw" + e.ToString());
                throw e;
            }
            finally
            {
                locker.Release();
            }
        }