Cryptan

Cryptan is a Rust toolkit for experimenting with the classic Caesar cipher. It provides a command-line interface and reusable library helpers for encrypting, decrypting, and brute-forcing ciphertext. Optional Python integration (via pyo3) uses the wordfreq package to score decoded results.

Features

• Encrypt plaintext with arbitrary rotation keys, including negative and >26 values.
• Decrypt ciphertext for a known key.
• Brute-force search possible keys, returning the most meaningful results first.
• Optional scoring of decoded text using Python's wordfreq frequencies.
• Usable as a CLI (caesar) or as a Rust library (cryptan).

Requirements

• Rust 1.70+ (edition 2021).
• Python 3.7+ with the wordfreq package installed when you want meaningfulness scoring.

Install the Python dependency with:

pip install wordfreq

If wordfreq is unavailable, brute-force output is still produced but without meaningfulness scores.

Installation

From source

Clone this repository and build the CLI locally:

cargo install --path .

This installs the caesar binary in your Cargo bin directory.

Library usage

Add the crate as a dependency in your Cargo.toml (use a path while developing locally):

[dependencies]
cryptan = { path = "../Cipher-helper" }

Command-line usage

List the available subcommands:

caesar --help

Encrypt plaintext with a key:

caesar encrypt 3 "attack at dawn"

Decrypt ciphertext when you know the key:

caesar decrypt 3 "dwwdfn dw gdzq"

Brute-force every rotation and rely on meaningfulness scoring (defaults to threshold 0.5):

caesar brute "ftue rcjj" --threshold 0.6

Show every decoded variant regardless of score:

caesar brute --all "ftue rcjj"

Library examples

Encrypt and decrypt in your own code using the convenience functions exported by cryptan:

use cryptan::{caesar_encrypt, caesar_decrypt};

let secret = caesar_encrypt("attack at dawn", 3);
assert_eq!(secret, "dwwdfn dw gdzq");

let recovered = caesar_decrypt(&secret, 3);
assert_eq!(recovered.text, "attack at dawn");

For advanced scenarios you can work directly with the CaesarCipher type and implement the Encrypt, Decrypt, or BruteForce traits.

Project layout

cryptan/
├── Cargo.toml
├── README.md
├── src/
│   ├── lib.rs
│   ├── main.rs
│   ├── caesar/
│   ├── traits.rs
│   └── utils/
│       └── py/
└── target/
    └── ...

Contributing

Issues and pull requests are welcome. Please ensure Rust code is formatted (cargo fmt) and passes clippy checks (cargo clippy) before submitting.

License

This project is currently unlicensed. Please add a license file before distributing binaries or publishing the crate.