RC4 Stream Cipher

This Rust crate implements the RC4 stream cipher, optimized for embedded use cases with no standard library dependencies (#![no_std]). The implementation ensures memory safety by forbidding unsafe code blocks. Additionally, a command-line utility is provided for file encryption and decryption using RC4.

Note: RC4 is known to be a broken encryption algorithm with several vulnerabilities. It is not recommended for use in security-critical applications.

Based on the book High Assurance Rust

Features

• No Standard Library Dependency: Suitable for embedded environments.
• Memory Safe: Uses Rust's safety guarantees by forbidding unsafe code.
• Flexible Key Length: Supports key lengths from 40 to 2048 bits.
• Simple API: Functions to initialize the cipher, generate keystream bytes, and apply the keystream to data.
• Command-Line Utility: Encrypt and decrypt files using the provided utility.
• Recursive File Processing: Encrypt or decrypt all files in a directory and its subdirectories.
• Large File Support: Buffering is used to handle files too large to fit into memory.

Usage

API

• Rc4::new(key: &[u8]) -> Self: Initializes a new RC4 instance with the provided key.
• Rc4::prga_next(&mut self) -> u8: Generates the next byte of the keystream.
• Rc4::apply_keystream(&mut self, data: &mut [u8]): Encrypts or decrypts the provided data in place.
• Rc4::apply_keystream_static(key: &[u8], data: &mut [u8]): A static method for one-shot encryption/decryption.

Testing

Unit tests are included to ensure the implementation's correctness. Run the tests with:

cargo test

Command-Line Utility

The command-line utility allows you to encrypt and decrypt files using the RC4 cipher.

Build the utility with:

cd rcli/
cargo install --path . 

Usage

rcli --file <FILE_NAME> --key <HEX_KEY_BYTES> [--recursive]

• --file: The file or directory to encrypt or decrypt.
• --key: The encryption/decryption key in hexadecimal byte format.
• --recursive: (Optional) If set, process all files in the specified directory and its subdirectories.

Example

Create a file secret.txt you want to encrypt and decrypt, and add contents in plaintext to it.

To Encrypt a file:

rcli --file secret.txt --key 0x4b 0x8e 0x29 0x87 0x80

To Decrypt a file:

rcli --file secret.txt --key 0x4b 0x8e 0x29 0x87 0x80

To Recursively Encrypt files in a directory:

rcli --file my_directory --key 0x4b 0x8e 0x29 0x87 0x80 --recursive

To Recursively Decrypt files in a directory:

rcli --file my_directory --key 0x4b 0x8e 0x29 0x87 0x80 --recursive

License

This project is licensed under the MIT License.