leona 0.1.0

LIONESS cipher construction
Documentation 
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# leona 

[![Crates.io Version](https://img.shields.io/crates/v/leona?style=flat-square)](https://crates.io/crates/leona)
[![Crates.io License](https://img.shields.io/crates/l/leona?style=flat-square)](https://choosealicense.com/licenses/mit/)
[![docs.rs](https://img.shields.io/docsrs/leona?style=flat-square)](https://docs.rs/leona)

Implementation of
[LIONESS](https://link.springer.com/content/pdf/10.1007/3-540-60865-6_48.pdf)
in Rust. Works with `no_std` and generic over hashes/ciphers.

## ☣️ Cryptographic hazmat ☣️

This crate is not battle tested and not audited. It exists as a learning
exercise. Use it at your own risk.

## LIONESS

LIONESS is a wide block cipher, constructed using a hash algorithm and a stream
cipher. From the paper:

> Each ciphertext bit depends on all the plaintext bits in a very complex way,
> which contributes to the cryptographic strength.

## Example use

You need a hash algorithm and a compatible stream cipher (compatible means that
the hash output has the same size as the stream cipher key):

```rust
use leona::{Lioness, ZeroIv};
use blake2::Blake2sMac256;
use chacha20::ChaCha20;

type Cipher = Lioness<ZeroIv<ChaCha20>, Blake2sMac256>;

let mut data = [0u8; 64];
data[..11].copy_from_slice(b"hello world");

let cipher = Cipher::new_dynamic(b"secret");
cipher.encrypt(&mut data);
assert_ne!(&data[..11], b"hello world");
cipher.decrypt(&mut data);
assert_eq!(&data[..11], b"hello world");
```

## Alternatives

There are two drawbacks to LIONESS:

1. It is slow.
2. It cannot encrypt short messages (shorther than the hash output size).

If you require a wide block cipher, consider using a different construction
(like aez via [aez](https://crates.io/crates/aez) or
[zears](https://crates.io/crates/zears)).

## License

This crate is licensed under the terms of the MIT license. You can find the full license text in LICENSE.