Initial Commit

TcpClient/Program.cs

@@ -0,0 +1,142 @@
+using System;
+using System.Diagnostics;
+using System.Net.Sockets;
+using System.Numerics;
+using System.Text;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Encryption;
+
+enum ConversationState
+{
+    Initial = 0,
+    RsaPublicKeyGiven,
+    AesKeySended,
+    RsaPublicKeySended,
+    AesKeyGiven
+}
+
+class TcpClientProgram
+{
+    static void Main(string[] args)
+    {
+        TcpClient client = new TcpClient();
+        client.Connect("127.0.0.1", 5000);
+        Console.WriteLine("Connected to server.");
+
+        NetworkStream stream = client.GetStream();
+        bool isRunning = true;
+        ConversationState state = ConversationState.Initial;
+        while (isRunning)
+        {
+            byte[] buffer = new byte[4096];
+            int bytesRead;
+
+            RsaPublicKey publicKey = null;
+            RsaPrivateKey privateKey = null;
+            string? aesKey = null;
+            
+            while ((bytesRead = stream.Read(buffer, 0, buffer.Length)) != 0)
+            {
+                string receivedData = Encoding.ASCII.GetString(buffer, 0, bytesRead);
+                Console.WriteLine("Received: " + receivedData);
+
+                // Split the message into command and data
+                string[] messageParts = receivedData.Split(new char[] { ':' }, 2);
+                if (messageParts.Length < 2) continue; // Ignore malformed messages
+
+                string command = messageParts[0];
+                string message = messageParts[1];
+
+                switch (command)
+                {
+                    case "PUBKEY":
+                        Console.WriteLine("Received RSA Public Key: " + message);
+                        state = ConversationState.RsaPublicKeyGiven;
+                        var json = Convert.FromBase64String(message);
+                        var dict = JsonSerializer.Deserialize<Dictionary<string, string>>(json);
+                        publicKey = new RsaPublicKey(BigInteger.Parse((string)dict["E"]),
+                            BigInteger.Parse((string)dict["N"]));
+                        break;
+                    case "AESKEY":
+                        Console.WriteLine("Received Encrypted AES Key: " + message);
+                        state = ConversationState.AesKeyGiven;
+                        aesKey = Encoding.UTF8.GetString(Convert.FromBase64String(message));
+                        break;
+                    case "MSG":
+                        Console.WriteLine("Received AES Encrypted Message: " + message);
+                        // todo: decrypt message and print it
+                        var decodedMessage = Convert.FromBase64String(message);
+                        var decryptedMessageBytes = RSA.Decrypt(privateKey, decodedMessage);
+                        Console.WriteLine($"Decrypted message: {Encoding.UTF8.GetString(decryptedMessageBytes)}");
+                        break;
+                    case "EXIT":
+                        Console.WriteLine("Client is disconnecting...");
+                        client.Close();
+                        return;
+                    default:
+                        Console.WriteLine("Unknown command received: " + command);
+                        break;
+                }
+            }
+
+            Console.WriteLine("1. Send RSA public key");
+            Console.WriteLine("4. Send AES key encrypted with RSA");
+            Console.WriteLine("5. Send/receive AES encrypted message");
+            Console.WriteLine("6. Exit");
+
+            string choice = Console.ReadLine();
+            if (state == ConversationState.RsaPublicKeyGiven && choice == "1")
+            {
+                Console.WriteLine("You already recieved Public Key from participant. It's time to send him your AES key back");
+                continue;
+            }
+
+            if (state == ConversationState.AesKeyGiven && choice == "4")
+            {
+                Console.WriteLine("You already have AES key from participant. It's time to send him encrypted message.");
+            }
+
+            switch (choice)
+            {
+                case "1":
+                    // Placeholder: Send a simulated RSA public key
+                    var json = publicKey.ToJsonString();
+                    var message = Convert.ToBase64String(Encoding.UTF8.GetBytes(json));
+                    SendMessage(stream, "PUBKEY", message);
+                    state = ConversationState.RsaPublicKeySended;
+                    break;
+                case "4":
+                    // Placeholder: Send an AES key encrypted with RSA
+                    aesKey = ""; //todo: generate random
+                    var aesKeyEncryptedBytes = RSA.Encrypt(publicKey, Encoding.UTF8.GetBytes(aesKey));
+                    SendMessage(stream, "AESKEY", Convert.ToBase64String(aesKeyEncryptedBytes));
+                    state = ConversationState.AesKeySended;
+                    break;
+                case "5":
+                    string msg = Console.ReadLine();
+                    // Placeholder: Send an AES encrypted message
+                    SendMessage(stream, "MSG", Convert.ToBase64String(RSA.Encrypt(publicKey, Encoding.UTF8.GetBytes(msg))));
+                    break;
+                case "6":
+                    SendMessage(stream, "EXIT", "Disconnecting");
+                    isRunning = false;
+                    Console.WriteLine("Exiting...");
+                    break;
+                default:
+                    Console.WriteLine("Invalid choice. Please try again.");
+                    break;
+            }
+        }
+
+        client.Close();
+    }
+
+    static void SendMessage(NetworkStream stream, string command, string message)
+    {
+        string formattedMessage = $"{command}:{message}";
+        byte[] data = Encoding.ASCII.GetBytes(formattedMessage);
+        stream.Write(data, 0, data.Length);
+        Console.WriteLine($"Sent [{command}]: {message}");
+    }
+}

TcpClient/TcpClient.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <OutputType>Exe</OutputType>
+        <TargetFramework>net8.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+    <ItemGroup>
+      <ProjectReference Include="..\Encryption\Encryption.csproj" />
+    </ItemGroup>
+
+</Project>