NOJSCAP

NOJSCAP is a minimal Proof-of-Work based CAPTCHA system. It includes both:

• A NOJSCAP client that computes valid nonces for challenge strings using SHA-256.
• A NOJSCAP server that issue challenges and verify solutions over HTTP.

This repository is structured as a monorepo containing both the client and server codebases.

Read project background: https://libroot.org/posts/project-nojscap/

---

Structure

.
├── client/    # Proof-of-Work nonce generator implementations
└── server/    # Server-side challenge issuers & verifiers

---

Client

The client directory includes NOJSCAP client implementations in multiple languages. Each version takes a challenge string and a difficulty level, then searches for a nonce such that the SHA-256 hash of challenge + nonce begins with the required number of leading zero bits.

Supported Languages

• C: nojscap.c
• Go: nojscap.go
• Python: nojscap.py
• JavaScript (Node.js): nojscap.js
• Rust: nojscap.rs

Each implementation is self-contained and demonstrates equivalent functionality.

---

Server

The server directory contains example implementations in multiple languages of NOJSCAP servers that issue PoW challenges and validate solutions.

Available Servers

• Python + Flask

cd server/python-html
python3 server.py

• TypeScript + Express

cd server/ts-express
npm install
npx tsx start

• Go + net/http

cd server/go-http
go run server.go

Each server implementation listens for challenge requests and verifies submitted nonces against the configured difficulty level.

---

License

GNU AGPLv3