Generic Output Feedback (OFB) mode implementation.

This crate implements OFB as a synchronous stream cipher.

Warning

This crate does not provide any authentification! Thus ciphertext integrity is not verified, which can lead to serious vulnerabilities!

Examples

extern crate aes;
extern crate ofb;
#[macro_use] extern crate hex_literal;

use aes::Aes128;
use ofb::Ofb;
use ofb::stream_cipher::{NewStreamCipher, SyncStreamCipher};

type AesOfb = Ofb<Aes128>;

let key = b"very secret key.";
let iv = b"unique init vect";
let plaintext = b"The quick brown fox jumps over the lazy dog.";
let ciphertext = hex!("
8f0cb6e8 9286cd02 09c95da4 fa663269
9455b0bb e346b653 ec0d44aa bece8cc9
f886df67 049d780d 9ccdf957
");

let mut buffer = plaintext.to_vec();
// create cipher instance
let mut cipher = AesOfb::new_var(key, iv).unwrap();
// apply keystream (encrypt)
cipher.apply_keystream(&mut buffer);
assert_eq!(buffer, &ciphertext[..]);
// and decrypt it back
AesOfb::new_var(key, iv).unwrap().apply_keystream(&mut buffer);
assert_eq!(buffer, &plaintext[..]);

// OFB mode can be used with streaming messages
let mut cipher = AesOfb::new_var(key, iv).unwrap();
for chunk in buffer.chunks_mut(3) {
cipher.apply_keystream(chunk);
}
assert_eq!(buffer, &ciphertext[..]);