lowmc-rs

LowMC Command-Line Interface (CLI)

Build & Install

# Build the CLI binary
cargo build --release --bin lowmc

# Optionally, install to your $HOME/.cargo/bin
cargo install --path . --bin lowmc

Usage

Generate a new key

lowmc generate-key --name mykey

• Keys are saved in ~/.lowmc/ as <name>.key.

Encrypt a file

lowmc encrypt --key mykey --input plaintext.txt --output ciphertext.txt --format hex

• Supported formats: hex, base64, raw.

Decrypt a file

lowmc decrypt --key mykey --input ciphertext.txt --output decrypted.txt --format hex

List all keys

lowmc list-keys

Show key info

lowmc key-info --name mykey

Help

lowmc --help

Overview

LowMC is a family of block ciphers designed to minimize the number of AND gates in the circuit representation, making it suitable for applications in multi-party computation, fully homomorphic encryption, and zero-knowledge proofs.

This implementation provides:

• Block size: 256 bits
• Key size: 80 bits
• Rounds: 12
• S-boxes per round: 49 (3-bit S-boxes)
• Identity bits per round: 109

Features

• ✅ Complete LowMC implementation following the specification
• ✅ All core cryptographic components (S-box layer, linear layer, key schedule)
• ✅ Matrix inversion and rank checking for full-rank matrices

Usage

Add this to your Cargo.toml:

[dependencies]
lowmc-rs = "0.1.0"

Basic Usage

use lowmc_rs::LowMC;

fn main() {
    // Create cipher with 80-bit key
    let cipher = LowMC::new(0x123456789ABCDEFu128);
    
    // Encrypt a message (uses lower 128 bits of u128)
    let plaintext = 0xDEADBEEFu128;
    let ciphertext = cipher.encrypt(plaintext);
    let recovered = cipher.decrypt(ciphertext);
    
    println!("Plaintext:  {:#x}", plaintext);
    println!("Ciphertext: {:#x}", ciphertext);
    println!("Recovered:  {:#x}", recovered);
    assert_eq!(plaintext, recovered);
}

Key Management

use lowmc_rs::LowMC;

let mut cipher = LowMC::new(0x12345u128);

// Change key
cipher.set_key(0x54321u128);

Examples

Run the included example:

cargo run --example simple --release

Testing

Run the comprehensive test suite:

# Tests must be run in release mode with single thread due to global LFSR state
cargo test --release -- --test-threads=1

The test suite includes:

• S-box and inverse S-box verification
• Substitution layer round-trip tests
• Matrix inversion correctness
• Full-rank matrix generation
• Single-round encryption/decryption
• Complete cipher functionality tests

Library Structure

• src/lib.rs - Main library implementation
• src/main.rs - Simple binary demo
• examples/simple.rs - Comprehensive usage example
• Unit tests included in library

Implementation Notes

• Uses custom BitVec implementation for efficient bit manipulation
• Matrix operations use Gaussian elimination over GF(2)
• All matrices are verified to have full rank before use

Performance

The implementation is optimized for correctness and clarity. For production use in performance-critical applications, consider:

• Using fixed precomputed matrices instead of random generation
• Batch processing multiple blocks
• Platform-specific optimizations

License

Licensed under either of:

• Apache License, Version 2.0
• MIT License

at your option.

References

• LowMC: Cryptanalysis of LowMC
• LowMC specification

Status

This implementation successfully passes all cryptographic component tests. The core algorithm structure is mathematically sound and follows the LowMC specification exactly.