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use block_cipher_trait::generic_array::{ArrayLength, GenericArray};
use block_cipher_trait::generic_array::typenum::{U8, Unsigned};
use block_cipher_trait::BlockCipher;
use block_padding::Padding;
use traits::{BlockMode, BlockModeError, BlockModeIv};
use utils::xor;
use core::mem;
use core::marker::PhantomData;
pub struct Ctr64<C, P>
where
C: BlockCipher<BlockSize = U8>,
P: Padding,
C::ParBlocks: ArrayLength<GenericArray<u8, U8>>,
{
cipher: C,
counter: u64,
_p: PhantomData<P>,
}
impl<C, P> BlockModeIv<C, P> for Ctr64<C, P>
where
C: BlockCipher<BlockSize = U8>,
P: Padding,
C::ParBlocks: ArrayLength<GenericArray<u8, U8>>,
{
fn new(cipher: C, nonce: &GenericArray<u8, C::BlockSize>) -> Self {
let counter = unsafe { mem::transmute_copy::<_, u64>(nonce).to_be() };
Self {
cipher,
counter,
_p: Default::default(),
}
}
}
impl<C, P> BlockMode<C, P> for Ctr64<C, P>
where
C: BlockCipher<BlockSize = U8>,
P: Padding,
C::ParBlocks: ArrayLength<GenericArray<u8, U8>>,
{
fn encrypt_nopad(
&mut self, buffer: &mut [u8]
) -> Result<(), BlockModeError> {
let bs = C::BlockSize::to_usize();
assert_eq!(buffer.len() % bs, 0);
for block in buffer.chunks_mut(bs) {
let res = self.counter.to_be();
self.counter = self.counter.wrapping_add(1);
let mut buf = unsafe { mem::transmute(res) };
self.cipher.encrypt_block(&mut buf);
xor(block, &buf);
}
Ok(())
}
fn decrypt_nopad(
&mut self, buffer: &mut [u8]
) -> Result<(), BlockModeError> {
self.encrypt_nopad(buffer)
}
}