# 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/](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**


```sh
cd server/python-html
python3 server.py
```

* **TypeScript + Express**


```sh
cd server/ts-express
npm install
npx tsx start
```

* **Go + net/http**


```sh
cd server/go-http
go run server.go
```

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

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## License

GNU AGPLv3