CO3099Assignment

Overview

This repository contains the coursework submission for the CO3099 module (University of Leicester). The project is implemented in Java and demonstrates practical skills in network programming, cryptography, file I/O, and secure client-server messaging.

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Table of Contents

• Features
• Skills & Technologies
• System Architecture
• Sample Workflows
• Professional Development
• License & Authorship

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Features

• Secure Client-Server Messaging

  • Implements a client and server exchanging encrypted and signed messages over a network socket.
  • Utilizes RSA and DES for encryption/decryption, and digital signatures for message verification.
  • Handles message delivery with signature verification and optional reply.

• Key Management & Generation

  • Tools for generating RSA key pairs (RSAKeyGen.java).
  • Loads and manages public/private keys from files.

• Symmetric & Asymmetric Encryption

  • Demonstrates DES key generation, message encryption/decryption (encryption.java).
  • Uses RSA for encrypting messages and verifying authenticity.

• File I/O & Streams

  • Reads and writes messages and keys to disk.
  • Demonstrates Java's DataInputStream/DataOutputStream for binary communication (streams.java, bytes.java).

• Modular Structure

  • Organized codebase in src/main/java/org/example for maintainability and clarity.

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Skills & Technologies

• Programming Language: Java
• Networking: TCP sockets, client-server architecture
• Cryptography: RSA, DES, digital signatures
• File I/O: Streams, serialization, reading/writing binary data
• Software Engineering: Modular design, separation of concerns, secure coding practices
• Version Control: Git & GitHub

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System Architecture

• Client (Client.java): Connects to server, authenticates, receives and verifies messages, sends encrypted and signed messages to other users.
• Server (Server.java): Listens for incoming connections, manages user messages, decrypts and verifies them, delivers stored messages to users.
• Key Utility (Keys.java, RSAKeyGen.java): Generates and loads RSA key pairs, manages keys for users and server.
• Encryption Utility (encryption.java): Provides DES-based symmetric encryption/decryption for file-stored messages.
• Supporting Utilities (streams.java, bytes.java): Demonstrates handling of bytes and file streams.

Directory Structure:

CO3099Assignment/
└── src/
    └── main/
        └── java/
            └── org/
                └── example/
                    ├── Client.java
                    ├── Server.java
                    ├── Keys.java
                    ├── RSAKeyGen.java
                    ├── encryption.java
                    ├── streams.java
                    ├── bytes.java

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Sample Workflows

1. Generate RSA Keys
   Run RSAKeyGen to generate key pairs for a user or server:

   java org.example.RSAKeyGen alice
   

   Creates alice.pub and alice.prv.

2. Start the Server
   Start the server and listen for connections:

   java org.example.Server <port>
   

3. Start the Client
   Connect client to server and authenticate:

   java org.example.Client <host> <port> <userId>
   

4. Send/Receive Secure Messages
   Client sends encrypted/signed messages. Server decrypts, verifies, and delivers messages securely.

5. Symmetric Encryption Demo
   Encrypt and decrypt messages using DES:

   java org.example.encryption -e    # Encrypt mode
   java org.example.encryption -d    # Decrypt mode
   

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Professional Development

Working on this project evidences:

• Proficiency in Java network and security programming
• Understanding of cryptographic protocols (RSA, DES, digital signatures)
• Secure handling of messages and key management
• Modular software architecture and version control
• Practical experience in problem-solving and technical documentation

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License & Authorship

This project is a coursework submission for CO3099 at University of Leicester. All code is original unless stated otherwise.

Author: gilo9
Module: CO3099, University of Leicester

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