work on SendMessage

client/Message.cs

@@ -0,0 +1,72 @@
+
+
+using System;
+using System.Collections.Generic;
+using System.Security.Cryptography;
+using System.Text;
+using lib;
+
+namespace client;
+
+public class Message
+{
+    public uint Id { set; get; }
+    public string Sender { set; get; }
+    public bool IsAck { set; get; }
+    public string Content { set; get; }
+    public byte[] Signature { set; get; }
+
+    public Message(byte[] bytes)
+    {
+        if (bytes[0] != 0)
+        {
+            Console.WriteLine("Failed parsing message, unsupported version");
+        }
+        // skip the first byte for simplicity
+        bytes = bytes[1..];
+        Id = BitConverter.ToUInt32(bytes, 0);
+        Sender = Utils.BytesToNumber(bytes[4..12]);
+        IsAck = bytes[12] != 0;
+        Content = Encoding.UTF8.GetString(bytes[13..(bytes.Length - 32)]);
+        Signature = bytes[(bytes.Length - 32)..];
+    }
+
+    public Message(uint Id, string Sender, bool IsAck, string Content)
+    {
+        this.Id = Id;
+        this.Sender = Sender;
+        this.IsAck = IsAck;
+        this.Content = Content;
+        Signature = [];
+    }
+
+    public void CalculateSignature(RSA key)
+    {
+        Signature = key.SignData(Bytes(false), HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
+    }
+
+    public bool IsSignatureValid(RSA key)
+    {
+        return key.VerifyData(Bytes(false), Signature, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
+    }
+
+    public byte[] Bytes(bool IncludeSignature = true)
+    {
+        List<byte> msg = [];
+        // 0..4
+        msg.AddRange(BitConverter.GetBytes(Id));
+        // 4..12
+        msg.AddRange(Utils.NumberToBytes(Sender));
+        // 12
+        msg.Add((byte)(IsAck ? 1 : 0));
+        // 13..(len - 32)
+        msg.AddRange(Encoding.UTF8.GetBytes(Content));
+        // (len - 32)..
+        if (IncludeSignature) // we dont want to include the signature when we sign/verify the data
+        {
+            msg.AddRange(Signature);
+        }
+
+        return [0, .. msg];
+    }
+}

client/Program.cs

@@ -289,7 +289,7 @@ public class Program
                 // even if we know who sent the message we dont know which message it is unless the server also knows
                 // and i dont want the server to be aware of that, i think it makes more sense for the server to act as a relay
                 // and a buffer than an actual participant, so if the message is failing to decrypt that will go unnoticed.
-                // supposedly the sender will notice the lack of ACK and send it again
+                // supposedly the sender will notice the lack of response and send it again
                 Console.WriteLine("Incoming message failed to decrypt, unknown sender");
             }
         }

server/Program.cs

@@ -240,6 +240,8 @@ public class Program
                         }
                         break;
                     case RequestType.SendMessage:
+                        string recv = Utils.BytesToNumber(msg[3..11]);
+                        int msgLen = BitConverter.ToInt32(msg, 11);
 
                         break;
                     default: