Yohu 🔐

A versatile command-line cryptography tool implementing multiple cipher algorithms for educational and practical use.

Features

• Caesar Cipher: Classic shift cipher with customizable shift values
• Vigenère Cipher: Polyalphabetic cipher using keyword-based encryption/decryption
• AES-128-CBC: Modern symmetric encryption with PKCS7 padding
• Caesar Cipher Cracking: Automatic cryptanalysis using Chi-squared frequency analysis
• Flexible Input: Support for direct text input or file-based processing
• File I/O: Save results to files for further use

Installation

From Crates.io

cargo install yohu

From Source

git clone <your-repository-url>
cd yohu
cargo build --release

Usage

Run the interactive CLI:

cargo run

The application will guide you through:

1. Choosing your cipher method
2. Providing necessary parameters (keys, shift values, etc.)
3. Selecting input method (direct text or file)
4. Processing and displaying results
5. Optionally saving output to a file

Cipher Options

1. Caesar Cipher

• Purpose: Simple substitution cipher
• Input: Shift amount (positive or negative integer)
• Example: Shift of 3 transforms 'A' → 'D'

2. Vigenère Cipher

• Purpose: Polyalphabetic substitution cipher
• Input: Keyword (alphabetic characters)
• Mode: Encryption or decryption
• Example: Keyword "KEY" creates repeating shift pattern

3. AES-128-CBC

• Purpose: Modern symmetric encryption
• Input:
  • 16-character secret key
  • 16-character initialization vector (IV)
• Mode: Encryption or decryption
• Output: Hex-encoded ciphertext for encryption

4. Caesar Cipher Cracking

• Purpose: Automatic cryptanalysis
• Method: Chi-squared frequency analysis against English letter frequencies
• Output: Best guess decryption and estimated shift key

Examples

Caesar Cipher Encryption

Input: "Hello World"
Shift: 3
Output: "Khoor Zruog"

Vigenère Cipher

Input: "HELLO"
Keyword: "KEY"
Output: "RIJVS"

AES-128-CBC

Input: "Secret Message"
Key: "MySecretKey12345"
IV: "MyInitVector1234"
Output: Hex-encoded ciphertext

Dependencies

• aes - AES block cipher implementation
• cbc - Cipher Block Chaining mode
• hex - Hexadecimal encoding/decoding

Security Notice

⚠️ Important: This tool is designed for educational purposes and experimentation. For production use:

• Use cryptographically secure random number generators for keys and IVs
• Consider more robust key derivation functions
• Implement proper key management practices
• Classical ciphers (Caesar, Vigenère) are not secure for real-world use

Contributing

Contributions are welcome! Please feel free to submit issues, feature requests, or pull requests.

Development Setup

1. Clone the repository
2. Install Rust (1.70+ recommended)
3. Run tests: cargo test
4. Build: cargo build

License

This project is licensed under the MIT License - see the LICENSE file for details.

Acknowledgments

• Frequency analysis implementation based on standard English letter frequencies
• AES implementation uses the RustCrypto project's aes and cbc crates

Yohu - Making cryptography accessible and educational! 🚀