block_modes/
cfb8.rs

1use crate::{
2    traits::{BlockMode, IvState},
3    utils::Block,
4};
5use block_padding::Padding;
6use cipher::{generic_array::GenericArray, BlockCipher, BlockEncrypt};
7use core::marker::PhantomData;
8
9/// [Cipher feedback][1] (CFB) block mode instance with a full block feedback.
10///
11/// [1]: https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_feedback_(CFB)
12#[derive(Clone)]
13pub struct Cfb8<C: BlockCipher + BlockEncrypt, P: Padding> {
14    cipher: C,
15    iv: GenericArray<u8, C::BlockSize>,
16    _p: PhantomData<P>,
17}
18
19impl<C, P> BlockMode<C, P> for Cfb8<C, P>
20where
21    C: BlockCipher + BlockEncrypt,
22    P: Padding,
23{
24    type IvSize = C::BlockSize;
25
26    fn new(cipher: C, iv: &Block<C>) -> Self {
27        Self {
28            cipher,
29            iv: iv.clone(),
30            _p: Default::default(),
31        }
32    }
33
34    fn encrypt_blocks(&mut self, blocks: &mut [Block<C>]) {
35        let mut iv = self.iv.clone();
36        let n = iv.len();
37        for block in blocks.iter_mut() {
38            for b in block.iter_mut() {
39                let iv_copy = iv.clone();
40                self.cipher.encrypt_block(&mut iv);
41                *b ^= iv[0];
42                iv[..n - 1].clone_from_slice(&iv_copy[1..]);
43                iv[n - 1] = *b;
44            }
45        }
46        self.iv = iv;
47    }
48
49    fn decrypt_blocks(&mut self, blocks: &mut [Block<C>]) {
50        let mut iv = self.iv.clone();
51        let n = iv.len();
52        for block in blocks.iter_mut() {
53            for b in block.iter_mut() {
54                let iv_copy = iv.clone();
55                self.cipher.encrypt_block(&mut iv);
56                let t = *b;
57                *b ^= iv[0];
58                iv[..n - 1].clone_from_slice(&iv_copy[1..]);
59                iv[n - 1] = t;
60            }
61        }
62        self.iv = iv;
63    }
64}
65
66impl<C, P> IvState<C, P> for Cfb8<C, P>
67where
68    C: BlockCipher + BlockEncrypt,
69    P: Padding,
70{
71    fn iv_state(&self) -> GenericArray<u8, Self::IvSize> {
72        self.iv.clone()
73    }
74}
block_modes/cfb8.rs

block_modes/
cfb8.rs
