Proof of Work Challenge-Response Server

A TCP server implementation protected from DDoS attacks using a Proof of Work (PoW) challenge-response protocol. After successfully solving the PoW challenge, the server sends a random quote from a collection.

How It Works

1. Client-Server Interaction:

   • Client connects and requests a quote
   • Server sends a PoW challenge
   • Client solves the challenge (finds a nonce that produces a hash with required leading zeros)
   • Server verifies the solution and sends a quote if valid

2. Proof of Work Implementation:

   • Uses SHA-256 hashing algorithm
   • Challenge includes random data and timestamp
   • Solution requires finding a nonce that produces a hash with N leading zeros
   • Current difficulty is set to 6 leading zeros (can be adjusted in internal/pow/pow.go)
   • Higher difficulty values require more computational work:

     // internal/pow/pow.go
     const (
         Difficulty = 6  // Increase this value for harder challenges
     )

3. DDoS Protection:

   • Each quote request requires significant computational work
   • Timestamp in challenge prevents replay attacks
   • CPU-intensive but memory-efficient
   • Easy to verify but time-consuming to solve

Running the Project

Prerequisites

• Go 1.23 or higher
• Make

Windows

• Download and install Go
• Download and install Make
• Use make build to build the project
• Use make run-all to run the server and client

Linux

• Install Go 1.23 or higher
• Use make build to build the project
• Use make run-all to run the server and client