public const int MAX_MESSAGELENGTH_RELAY = 3 + 2 + 16 * 1024; //! bytes (+3 for OP_NOP OP_NOP OP_RETURN, +2 for the pushdata opcodes)
public Script GenerateScriptPubKey(string message, string messageRecipient, string replyToAddress, string rewardAddress, bool encryptMessage, RsaPublicKey publicKey, RsaPrivateKey privateKey)
{
byte[] pushData = null;
var wsm = new WantedSystemMessage()
{
Encryption = (encryptMessage ? MessageEncryption.RSA4096AES256 : MessageEncryption.None),
Text = message,
Metadata = new WantedSystemMessageMetadata()
{
CreationTimeUtc = DateTime.UtcNow.ToString(),
RecipientAddress = messageRecipient,
ReplyToAddress = replyToAddress,
RewardAddress = rewardAddress
}
};
if (encryptMessage)
{
pushData = GenerateWantedSystemMessagePushData(wsm, publicKey);
}
else
{
pushData = GenerateWantedSystemMessagePushData(wsm);
}
return(GenerateScriptPubKey(pushData));
}
private byte[] GenerateWantedSystemMessagePushData(WantedSystemMessage message, RsaPublicKey publicKey = null)
{
byte[] encryptionKey = new byte[0];
string metadata = JsonConvert.SerializeObject(message.Metadata);
byte[] uncompressedMetadata = System.Text.Encoding.UTF8.GetBytes(metadata);
byte[] compressedMetadata = GZIPCompressByteArray(uncompressedMetadata);
byte[] uncompressedMessage = System.Text.Encoding.UTF8.GetBytes(message.Text);
if (message.Encryption == MessageEncryption.RSA4096AES256)
{
byte[] aesKey = GetRandomData(256);
encryptionKey = RSAEncryptByteArray(aesKey, publicKey);
byte[] encryptedMessage = AESEncryptByteArray(uncompressedMessage, aesKey);
uncompressedMessage = encryptedMessage;
}
byte[] compressedMessage = GZIPCompressByteArray(uncompressedMessage);
byte[] header = System.Text.Encoding.UTF8.GetBytes("TWS");
byte version = (byte)message.Version;
byte compression = (byte)message.Compression;
byte checksumType = (byte)message.ChecksumType;
byte encryptionType = (byte)message.Encryption;
ushort encryptionKeyLength = (ushort)encryptionKey.Length;
ushort metadataLength = (ushort)compressedMetadata.Length;
ushort messageLength = (ushort)compressedMessage.Length;
List <byte> pushDataList = new List <byte>();
pushDataList.AddRange(header);
pushDataList.Add(version);
pushDataList.Add(compression);
pushDataList.Add(checksumType);
pushDataList.Add(encryptionType);
pushDataList.AddRange(BitConverter.GetBytes(encryptionKeyLength));
pushDataList.AddRange(BitConverter.GetBytes(metadataLength));
pushDataList.AddRange(BitConverter.GetBytes(messageLength));
pushDataList.AddRange(encryptionKey);
pushDataList.AddRange(compressedMetadata);
pushDataList.AddRange(compressedMessage);
if (pushDataList.Count > 16 * 1024)
{
throw new Exception("Push data can't be bigger than 16 kbytes.");
}
return(pushDataList.ToArray());
}
public WantedSystemMessage GetWantedSystemMessage(Script scriptPubKey, RsaPrivateKey privateKey = null)
{
var msg = new WantedSystemMessage();
if (scriptPubKey.Length < 13)
{
throw new Exception("This ScriptPubKey is not a valid Wanted System message.");
}
Op[] scriptPubKeyOps = scriptPubKey.ToOps().ToArray();
if ((scriptPubKeyOps[0].Code != OpcodeType.OP_NOP) || (scriptPubKeyOps[1].Code != OpcodeType.OP_NOP) || (scriptPubKeyOps[2].Code != OpcodeType.OP_RETURN))
{
throw new Exception("This ScriptPubKey is not a valid Wanted System message.");
}
byte[] pd = scriptPubKeyOps[3].PushData;
byte[] header = pd.Take <byte>(3).ToArray();
msg.Version = pd[3];
if (msg.Version != 1)
{
throw new Exception($"Wanted System message vesion {msg.Version} is not supported.");
}
msg.Compression = (MessageCompression)pd[4];
if (msg.Compression != MessageCompression.GZip)
{
throw new Exception($"Wanted System message compression {msg.Compression} is not supported.");
}
msg.ChecksumType = (MessageChecksum)pd[5];
if (msg.ChecksumType != MessageChecksum.None)
{
throw new Exception($"Wanted System message checksum {msg.ChecksumType} is not supported.");
}
msg.Encryption = (MessageEncryption)pd[6];
if (msg.Encryption != MessageEncryption.RSA4096AES256)
{
throw new Exception($"Wanted System message encryption {msg.Encryption} is not supported.");
}
ushort encryptionKeyLength = BitConverter.ToUInt16(pd, 7);
ushort metadataLength = BitConverter.ToUInt16(pd, 9);
ushort messageLength = BitConverter.ToUInt16(pd, 11);
byte[] encryptionKey = new byte[encryptionKeyLength];
byte[] compressedMetadata = new byte[metadataLength];
byte[] compressedMessage = new byte[messageLength];
Array.Copy(pd, 13, encryptionKey, 0, encryptionKeyLength);
Array.Copy(pd, 13 + encryptionKeyLength, compressedMetadata, 0, metadataLength);
Array.Copy(pd, 13 + encryptionKeyLength + metadataLength, compressedMessage, 0, messageLength);
byte[] uncompressedMetadata = GZIPDecompressByteArray(compressedMetadata);
byte[] uncompressedMessage = GZIPDecompressByteArray(compressedMessage);
// process metadata using json serializer
string metadata = System.Text.Encoding.UTF8.GetString(uncompressedMetadata);
msg.Metadata = JsonConvert.DeserializeObject <WantedSystemMessageMetadata>(metadata);
// Decrypt the message if needed
if (msg.Encryption == MessageEncryption.RSA4096AES256)
{
if (privateKey == null)
{
throw new Exception("The message is encrypted but the decryption key was not provided.");
}
byte[] aesKey = null;
try
{
aesKey = RSADecryptByteArray(encryptionKey, privateKey);
}
catch
{
throw new Exception("The private key you provided isn't a match for the public key the message was encrypted with.");
}
uncompressedMessage = AESDecryptByteArray(uncompressedMessage, aesKey);
}
msg.Text = System.Text.Encoding.UTF8.GetString(uncompressedMessage);
return(msg);
}