strobe-rs

This is a pure Rust, no_std implementation of the Strobe protocol framework. The designer's description:

Strobe is a new framework for cryptographic protocols. It can also be used for regular encryption. Its goals are to make cryptographic protocols much simpler to develop, deploy and analyze; and to fit into even tiny IoT devices. To that end, it uses only one block function — Keccak-f — to encrypt and authenticate messages.

This implementation currently only supports Keccak-f[1600] (the highest security level) as the internal permutation function.

Example

A simple example that does authenticated encryption and decryption:

use strobe_rs::{SecParam, Strobe};

use rand::RngCore;

// NOTE: This is just a simple authenticated encryption scheme. For a robust AEAD construction,
// see the example at https://strobe.sourceforge.io/examples/aead/

fn main() {
    let mut rng = rand::thread_rng();

    // Sender and receiver
    let mut tx = Strobe::new(b"correctnesstest", SecParam::B256);
    let mut rx = Strobe::new(b"correctnesstest", SecParam::B256);

    // Key both sides with a predetermined key
    let k = b"the-combination-on-my-luggage";
    tx.key(k, false);
    rx.key(k, false);

    // Have the transmitter sample and send a nonce (192 bits) in the clear
    let mut nonce = [0u8; 24];
    rng.fill_bytes(&mut nonce);
    rx.recv_clr(&nonce, false);
    tx.send_clr(&nonce, false);

    // Have the transmitter send an authenticated ciphertext (with a 256 bit MAC)
    let orig_msg = b"groceries: kaymac, ajvar, cream, diced onion, red pepper, grilled meat";
    let mut msg_buf = *orig_msg;
    tx.send_enc(&mut msg_buf, false);
    let mut mac = [0u8; 32];
    tx.send_mac(&mut mac, false);

    // Rename for clarity. `msg_buf` has been encrypted in-place.
    let mut ciphertext = msg_buf;

    // Have the receiver receive the ciphertext and MAC
    rx.recv_enc(ciphertext.as_mut_slice(), false);
    let res = rx.recv_mac(&mac);

    // Check that the MAC verifies
    assert!(res.is_ok());
    // Check that the decrypted ciphertext equals the original plaintext
    let round_trip_msg = ciphertext;
    assert_eq!(&round_trip_msg, orig_msg);
}

Features

Default features flags: none

Feature flag list:

• std — Implements std::error::Error for AuthError.
• asm — Enables optimized assembly for the Keccak permutation, if available. Assembly currently only exists for ARMv8.
• serialize_secret_state — Implements serde's Serialize and Deserialize traits for the Strobe struct. SECURITY NOTE: Serializing Strobe state outputs security sensitive data that MUST be kept private. Treat the data as you would a private encryption/decryption key.

For info on how to omit or include feature flags, see the cargo docs on features.

MSRV

The current minimum supported Rust version (MSRV) is 1.60.0 (2022-04-04).

Tests

To run tests, execute

cargo test --features "std"

This includes known-answer tests, which test against JSON-encoded test vectors in the kat/ directory. To verify these test vectors against the reference Python implementation, cd into kat/, run python2 verify_test_vector.py and follow the included instructions.

Benchmarks

To benchmark, run

cargo bench

This will produce a summary with plots in target/crieteron/report/index.html. These won't be very interesting, since almost every function in STROBE has the same runtime.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option.

Warning

This code has not been audited in any sense of the word. Use at your own discretion.