public EncryptedKeyResult(BitcoinEncryptedSecretEC key, BitcoinAddress address, byte[] seed,
Func <BitcoinConfirmationCode> calculateConfirmation)
{
this.EncryptedKey = key;
this.GeneratedAddress = address;
this._CalculateConfirmation = calculateConfirmation;
this.Seed = seed;
}
public bool Check(string passphrase, BitcoinAddress expectedAddress)
{
//Derive passfactor using scrypt with ownerentropy and the user's passphrase and use it to recompute passpoint
var passfactor =
BitcoinEncryptedSecretEC.CalculatePassFactor(passphrase, this.LotSequence, this.OwnerEntropy);
//Derive decryption key for pointb using scrypt with passpoint, addresshash, and ownerentropy
var passpoint = BitcoinEncryptedSecretEC.CalculatePassPoint(passfactor);
var derived =
BitcoinEncryptedSecretEC.CalculateDecryptionKey(passpoint, this.AddressHash, this.OwnerEntropy);
//Decrypt encryptedpointb to yield pointb
var pointbprefix = this.EncryptedPointB[0];
pointbprefix = (byte)(pointbprefix ^ (byte)(derived[63] & 0x01));
//Optional since ArithmeticException will catch it, but it saves some times
if (pointbprefix != 0x02 && pointbprefix != 0x03)
{
return(false);
}
var pointb = BitcoinEncryptedSecret.DecryptKey(this.EncryptedPointB.Skip(1).ToArray(), derived);
pointb = new[] { pointbprefix }.Concat(pointb).ToArray();
//4.ECMultiply pointb by passfactor. Use the resulting EC point as a public key
var curve = ECKey.Secp256k1;
ECPoint pointbec;
try
{
pointbec = curve.Curve.DecodePoint(pointb);
}
catch (ArgumentException)
{
return(false);
}
catch (ArithmeticException)
{
return(false);
}
var pubkey = new PubKey(pointbec.Multiply(new BigInteger(1, passfactor)).GetEncoded());
//and hash it into address using either compressed or uncompressed public key methodology as specifid in flagbyte.
pubkey = this.IsCompressed ? pubkey.Compress() : pubkey.Decompress();
var actualhash = BitcoinEncryptedSecretEC.HashAddress(pubkey.GetAddress(this.Network));
var expectedhash = BitcoinEncryptedSecretEC.HashAddress(expectedAddress);
return(Utils.ArrayEqual(actualhash, expectedhash));
}
public EncryptedKeyResult GenerateEncryptedSecret(bool isCompressed = true, byte[] seedb = null)
{
//Set flagbyte.
byte flagByte = 0;
//Turn on bit 0x20 if the Bitcoin address will be formed by hashing the compressed public key
flagByte |= isCompressed ? (byte)0x20 : (byte)0x00;
flagByte |= this.LotSequence != null ? (byte)0x04 : (byte)0x00;
//Generate 24 random bytes, call this seedb. Take SHA256(SHA256(seedb)) to yield 32 bytes, call this factorb.
seedb = seedb ?? RandomUtils.GetBytes(24);
var factorb = Hashes.Hash256(seedb).ToBytes();
//ECMultiply passpoint by factorb.
var curve = ECKey.Secp256k1;
var passpoint = curve.Curve.DecodePoint(this.Passpoint);
var pubPoint = passpoint.Multiply(new BigInteger(1, factorb));
//Use the resulting EC point as a public key
var pubKey = new PubKey(pubPoint.GetEncoded());
//and hash it into a Bitcoin address using either compressed or uncompressed public key
//This is the generated Bitcoin address, call it generatedaddress.
pubKey = isCompressed ? pubKey.Compress() : pubKey.Decompress();
//call it generatedaddress.
var generatedaddress = pubKey.GetAddress(this.Network);
//Take the first four bytes of SHA256(SHA256(generatedaddress)) and call it addresshash.
var addresshash = BitcoinEncryptedSecretEC.HashAddress(generatedaddress);
//Derive a second key from passpoint using scrypt
//salt is addresshash + ownerentropy
var derived =
BitcoinEncryptedSecretEC.CalculateDecryptionKey(this.Passpoint, addresshash, this.OwnerEntropy);
//Now we will encrypt seedb.
var encrypted = BitcoinEncryptedSecret.EncryptSeed
(seedb,
derived);
//0x01 0x43 + flagbyte + addresshash + ownerentropy + encryptedpart1[0...7] + encryptedpart2 which totals 39 bytes
var bytes =
new[] { flagByte }
.Concat(addresshash)
.Concat(this.OwnerEntropy)
.Concat(encrypted.Take(8).ToArray())
.Concat(encrypted.Skip(16).ToArray())
.ToArray();
var encryptedSecret = new BitcoinEncryptedSecretEC(bytes, this.Network);
return(new EncryptedKeyResult(encryptedSecret, generatedaddress, seedb, () =>
{
//ECMultiply factorb by G, call the result pointb. The result is 33 bytes.
var pointb = new Key(factorb).PubKey.ToBytes();
//The first byte is 0x02 or 0x03. XOR it by (derivedhalf2[31] & 0x01), call the resulting byte pointbprefix.
var pointbprefix = (byte)(pointb[0] ^ (byte)(derived[63] & 0x01));
var pointbx = BitcoinEncryptedSecret.EncryptKey(pointb.Skip(1).ToArray(), derived);
var encryptedpointb = new[] { pointbprefix }.Concat(pointbx).ToArray();
var confirmBytes = this.Network.GetVersionBytes(Base58Type.CONFIRMATION_CODE, true)
.Concat(new[] { flagByte })
.Concat(addresshash)
.Concat(this.OwnerEntropy)
.Concat(encryptedpointb)
.ToArray();
return new BitcoinConfirmationCode(Encoders.Base58Check.EncodeData(confirmBytes), this.Network);
}));
}
