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#![no_std]
#[macro_use]
extern crate opaque_debug;
pub extern crate block_cipher_trait;
pub use block_cipher_trait::BlockCipher;
use block_cipher_trait::InvalidKeyLength;
use block_cipher_trait::generic_array::GenericArray;
use block_cipher_trait::generic_array::typenum::{U1, U8, U32};
use core::fmt;
mod consts;
use consts::PI_TABLE;
pub struct Rc2 {
exp_key: [u16; 64],
}
impl Rc2 {
pub fn new_with_eff_key_len(key: &[u8], eff_key_len: usize) -> Self {
Self {
exp_key: Rc2::expand_key(key, eff_key_len)
}
}
fn expand_key(key: &[u8], t1: usize) -> [u16; 64] {
let key_len = key.len() as usize;
let t8: usize = (t1+7)>>3;
let tm: usize = (255 % ((2 as u32).pow((8+t1-8*t8) as u32))) as usize;
let mut key_buffer: [u8; 128] = [0; 128];
key_buffer[..key_len].copy_from_slice(&key[..key_len]);
for i in key_len..128 {
let pos: u32 = (key_buffer[i-1] as u32 + key_buffer[i-key_len] as u32) & 0xff;
key_buffer[i] = PI_TABLE[pos as usize];
}
key_buffer[128-t8] = PI_TABLE[(key_buffer[128-t8] & tm as u8) as usize];
for i in (0..128-t8).rev() {
let pos: usize = (key_buffer[i+1] ^ key_buffer[i+t8]) as usize;
key_buffer[i] = PI_TABLE[pos];
}
let mut result: [u16; 64] = [0; 64];
for i in 0..64 {
result[i] = ((key_buffer[2*i+1] as u16) << 8) + (key_buffer[2*i] as u16)
}
result
}
fn mix(&self, r: &mut [u16; 4], j: &mut usize) {
r[0] = r[0].wrapping_add(self.exp_key[*j]).wrapping_add(r[3] & r[2]).wrapping_add(!r[3] & r[1]);
*j += 1;
r[0] = (r[0] << 1) | (r[0] >> 15);
r[1] = r[1].wrapping_add(self.exp_key[*j]).wrapping_add(r[0] & r[3]).wrapping_add(!r[0] & r[2]);
*j += 1;
r[1] = (r[1] << 2) | (r[1] >> 14);
r[2] = r[2].wrapping_add(self.exp_key[*j]).wrapping_add(r[1] & r[0]).wrapping_add(!r[1] & r[3]);
*j += 1;
r[2] = (r[2] << 3) | (r[2] >> 13);
r[3] = r[3].wrapping_add(self.exp_key[*j]).wrapping_add(r[2] & r[1]).wrapping_add(!r[2] & r[0]);
*j += 1;
r[3] = (r[3] << 5) | (r[3] >> 11);
}
fn mash(&self, r: &mut [u16; 4]) {
r[0] = r[0].wrapping_add(self.exp_key[(r[3] & 63) as usize]);
r[1] = r[1].wrapping_add(self.exp_key[(r[0] & 63) as usize]);
r[2] = r[2].wrapping_add(self.exp_key[(r[1] & 63) as usize]);
r[3] = r[3].wrapping_add(self.exp_key[(r[2] & 63) as usize]);
}
fn reverse_mix(&self, r: &mut [u16; 4], j: &mut usize) {
r[3] = (r[3] << 11) | (r[3] >> 5);
r[3] = r[3].wrapping_sub(self.exp_key[*j]).wrapping_sub(r[2] & r[1]).wrapping_sub(!r[2] & r[0]);
*j -= 1;
r[2] = (r[2] << 13) | (r[2] >> 3);
r[2] = r[2].wrapping_sub(self.exp_key[*j]).wrapping_sub(r[1] & r[0]).wrapping_sub(!r[1] & r[3]);
*j -= 1;
r[1] = (r[1] << 14) | (r[1] >> 2);
r[1] = r[1].wrapping_sub(self.exp_key[*j]).wrapping_sub(r[0] & r[3]).wrapping_sub(!r[0] & r[2]);
*j -= 1;
r[0] = (r[0] << 15) | (r[0] >> 1);
r[0] = r[0].wrapping_sub(self.exp_key[*j]).wrapping_sub(r[3] & r[2]).wrapping_sub(!r[3] & r[1]);
*j = j.wrapping_sub(1);
}
fn reverse_mash(&self, r: &mut [u16; 4]) {
r[3] = r[3].wrapping_sub(self.exp_key[(r[2] & 63) as usize]);
r[2] = r[2].wrapping_sub(self.exp_key[(r[1] & 63) as usize]);
r[1] = r[1].wrapping_sub(self.exp_key[(r[0] & 63) as usize]);
r[0] = r[0].wrapping_sub(self.exp_key[(r[3] & 63) as usize]);
}
fn encrypt(&self, block: &mut GenericArray<u8, U8>) {
let mut r: [u16; 4] = [
((block[1] as u16) << 8) + (block[0] as u16),
((block[3] as u16) << 8) + (block[2] as u16),
((block[5] as u16) << 8) + (block[4] as u16),
((block[7] as u16) << 8) + (block[6] as u16),
];
let mut j = 0;
for i in 0..16 {
self.mix(&mut r, &mut j);
if i == 4 || i == 10 {
self.mash(&mut r);
}
}
block[0] = (r[0] & 0xff) as u8;
block[1] = (r[0] >> 8) as u8;
block[2] = (r[1] & 0xff) as u8;
block[3] = (r[1] >> 8) as u8;
block[4] = (r[2] & 0xff) as u8;
block[5] = (r[2] >> 8) as u8;
block[6] = (r[3] & 0xff) as u8;
block[7] = (r[3] >> 8) as u8;
}
fn decrypt(&self, block: &mut GenericArray<u8, U8>) {
let mut r: [u16; 4] = [
((block[1] as u16) << 8) + (block[0] as u16),
((block[3] as u16) << 8) + (block[2] as u16),
((block[5] as u16) << 8) + (block[4] as u16),
((block[7] as u16) << 8) + (block[6] as u16),
];
let mut j = 63;
for i in 0..16 {
self.reverse_mix(&mut r, &mut j);
if i == 4 || i == 10 {
self.reverse_mash(&mut r);
}
}
block[0] = r[0] as u8;
block[1] = (r[0] >> 8) as u8;
block[2] = r[1] as u8;
block[3] = (r[1] >> 8) as u8;
block[4] = r[2] as u8;
block[5] = (r[2] >> 8) as u8;
block[6] = r[3] as u8;
block[7] = (r[3] >> 8) as u8;
}
}
impl BlockCipher for Rc2 {
type KeySize = U32;
type BlockSize = U8;
type ParBlocks = U1;
fn new(key: &GenericArray<u8, U32>) -> Self {
Self::new_varkey(key).unwrap()
}
fn new_varkey(key: &[u8]) -> Result<Self, InvalidKeyLength> {
if key.len() < 1 || key.len() > 128 {
Err(InvalidKeyLength)
} else {
Ok(Self::new_with_eff_key_len(key, key.len()*8))
}
}
fn encrypt_block(&self, block: &mut GenericArray<u8, U8>) {
self.encrypt(block);
}
fn decrypt_block(&self, block: &mut GenericArray<u8, U8>) {
self.decrypt(block);
}
}
impl_opaque_debug!(Rc2);