selevit / word_of_wisdom

Proof-of-work based challenge-response TCP server

Exersice

Design and implement “Word of Wisdom” tcp server.

• TCP server should be protected from DDOS attacks with the Prof of Work, the challenge-response protocol should be used.
• The choice of the POW algorithm should be explained.
• After Prof Of Work verification, the server should send one of the quotes from “Word of wisdom” book or any other collection of the quotes.
• Docker file should be provided both for the server and for the client that solves the POW challenge

How to run

docker-compose up -d
docker-compose run client

The server uses the Hashcash proof of work algorithm with default complexity equals to 4. When running a server, you can set custom puzzle complexity:

PUZZLE_COMPLEXITY=5 docker-compose up -d

If you pass RUST_LOG=debug to the client, you will be able to see the hashes it tries to solve the puzzle. But it can slow down the solving process.

RUST_LOG=debug docker-compose run client

Why Hashcash?

It uses a commonly known sha256 hash function, which makes the client implementation very simple. Also this is the most known proof-of-work algorithm, which is used in Bitcoin's mining.