private string CreateForwardMessage(Guid remoteId, string message)
{
byte[] iv = diffieHellman.GenerateIV();
byte[] encryptedChatMessage = diffieHellman.Encrypt(commonSecret[remoteId], message, iv);
string signature = HMACFactory.CreateSignature(Convert.ToBase64String(encryptedChatMessage), commonSecret[remoteId]);
return(MessageFactory.CreateForwardMessage(id, remoteId, iv, signature, encryptedChatMessage));
}
public override IAlgorithmElement CreateAlgorithmElement()
{
IMac hmac = HMACFactory.CreateDigets(Name);
switch (hmac.AlgorithmName)
{
default:
return(new HMACControl(hmac));
}
}
private string HandleDataAsync(string data)
{
//TODO
string[] dataArray = data.Split(';');
if (dataArray[0] == "PUBLICKEYACCEPT")
{
byte[] serverPublicKey = Convert.FromBase64String(dataArray[PackageLocation.PUBLICKEYACCEPT.PUBLIC_KEY]);
GetCommonSecretServer(serverPublicKey);
return("---Established secure connection with server.");
}
string decryptedPackage = diffieHellman.Decrypt(commonSecretServer,
Convert.FromBase64String(dataArray[PackageLocation.SECURE_PACKAGE.ENCRYPTED_DATA]),
Convert.FromBase64String(dataArray[PackageLocation.SECURE_PACKAGE.IV]));
string[] decryptedPackageArray = decryptedPackage.Split(';');
Guid senderId;
Guid remoteId;
string remoteUsername;
byte[] receiverPublicKey;
switch (decryptedPackageArray[0])
{
case "LOGINACCEPT":
id = new Guid(decryptedPackageArray[PackageLocation.LOGINACCEPT.ASSIGNED_ID]);
return("---Assigned ID: " + decryptedPackageArray[1]);
case "NEWUSER":
remoteId = new Guid(decryptedPackageArray[PackageLocation.NEWUSER.REMOTE_ID]);
remoteUsername = decryptedPackageArray[PackageLocation.NEWUSER.USERNAME];
AddUser(remoteId, remoteUsername);
return("---User " + remoteUsername + " has connected.");
case "LOADUSER":
remoteId = new Guid(decryptedPackageArray[PackageLocation.NEWUSER.REMOTE_ID]);
remoteUsername = decryptedPackageArray[PackageLocation.NEWUSER.USERNAME];
AddUser(remoteId, remoteUsername);
sendPublicKey(remoteId);
return("---Loaded user " + remoteUsername);
case "USERLEFT":
remoteId = new Guid(decryptedPackageArray[PackageLocation.NEWUSER.REMOTE_ID]);
remoteUsername = onlineUsernames[remoteId];
RemoveUser(remoteId);
return("---User " + remoteUsername + " left.");
case "FORWARDPUBLICKEYREQUEST":
senderId = new Guid(decryptedPackageArray[PackageLocation.FORWARDPUBLICKEYREQUEST.SENDER_ID]);
receiverPublicKey = Convert.FromBase64String(decryptedPackageArray[PackageLocation.FORWARDPUBLICKEYREQUEST.PUBLIC_KEY]);
GetCommonSecret(senderId, receiverPublicKey);
respondToPublicKey(senderId);
return("---Received key from " + onlineUsernames[senderId]);
case "FORWARDPUBLICKEYACCEPT":
senderId = new Guid(decryptedPackageArray[PackageLocation.FORWARDPUBLICKEYACCEPT.SENDER_ID]);
receiverPublicKey = Convert.FromBase64String(decryptedPackageArray[PackageLocation.FORWARDPUBLICKEYACCEPT.PUBLIC_KEY]);
GetCommonSecret(senderId, receiverPublicKey);
return("---Accepted key from " + onlineUsernames[senderId]);
case "FORWARD":
senderId = new Guid(decryptedPackageArray[PackageLocation.FORWARD.SENDER_ID]);
string signature = decryptedPackageArray[PackageLocation.FORWARD.SIGNATURE];
string encryptedData = decryptedPackageArray[PackageLocation.FORWARD.ENCRYPTED_DATA];
if (!HMACFactory.CheckSignature(encryptedData, commonSecret[senderId], signature))
{
return("---NOTE: received message with invalid signature.");
}
string decryptedData = diffieHellman.Decrypt(commonSecret[senderId],
Convert.FromBase64String(encryptedData),
Convert.FromBase64String(decryptedPackageArray[PackageLocation.FORWARD.IV]));
string[] decryptedDataArray = decryptedData.Split(';');
switch (decryptedDataArray[0])
{
case "CHATMESSAGE":
return(FormatChatMessage(decryptedDataArray));
case "FILE":
string fileName = decryptedDataArray[PackageLocation.FILE.FILE_NAME];
string userName = decryptedDataArray[PackageLocation.FILE.USERNAME];
byte[] rawFile = Convert.FromBase64String(decryptedDataArray[PackageLocation.FILE.RAW_FILE]);
SaveFile(fileName, rawFile);
return("---Received file from " + userName + " and saved as " + fileName);
}
return("...");
}
return("...");
}