#![no_std]
#![doc(
html_logo_url = "https://raw.githubusercontent.com/RustCrypto/media/26acc39f/logo.svg",
html_favicon_url = "https://raw.githubusercontent.com/RustCrypto/media/26acc39f/logo.svg",
html_root_url = "https://docs.rs/idea/0.5.1"
)]
#![deny(unsafe_code)]
#![cfg_attr(docsrs, feature(doc_cfg))]
#![warn(missing_docs, rust_2018_idioms)]
#![allow(clippy::many_single_char_names)]
pub use cipher;
use cipher::{
consts::{U16, U8},
inout::InOut,
AlgorithmName, Block, BlockCipher, Key, KeyInit, KeySizeUser,
};
use core::fmt;
#[cfg(feature = "zeroize")]
use cipher::zeroize::{Zeroize, ZeroizeOnDrop};
mod consts;
#[cfg(test)]
mod tests;
use consts::{FUYI, LENGTH_SUB_KEYS, MAXIM, ONE, ROUNDS};
#[derive(Clone)]
pub struct Idea {
enc_keys: [u16; LENGTH_SUB_KEYS],
dec_keys: [u16; LENGTH_SUB_KEYS],
}
impl Idea {
fn expand_key(&mut self, key: &Key<Self>) {
let length_key = key.len();
for i in 0..(length_key / 2) {
self.enc_keys[i] = (u16::from(key[2 * i]) << 8) + u16::from(key[2 * i + 1]);
}
let mut a: u16;
let mut b: u16;
for i in (length_key / 2)..LENGTH_SUB_KEYS {
if (i + 1) % 8 == 0 {
a = self.enc_keys[i - 15];
} else {
a = self.enc_keys[i - 7];
}
if (i + 2) % 8 < 2 {
b = self.enc_keys[i - 14];
} else {
b = self.enc_keys[i - 6];
}
self.enc_keys[i] = (a << 9) + (b >> 7);
}
}
fn invert_sub_keys(&mut self) {
let mut k = ROUNDS * 6;
for i in 0..=ROUNDS {
let j = i * 6;
let l = k - j;
let (m, n) = if i > 0 && i < 8 { (2, 1) } else { (1, 2) };
self.dec_keys[j] = self.mul_inv(self.enc_keys[l]);
self.dec_keys[j + 1] = self.add_inv(self.enc_keys[l + m]);
self.dec_keys[j + 2] = self.add_inv(self.enc_keys[l + n]);
self.dec_keys[j + 3] = self.mul_inv(self.enc_keys[l + 3]);
}
k = (ROUNDS - 1) * 6;
for i in 0..ROUNDS {
let j = i * 6;
let l = k - j;
self.dec_keys[j + 4] = self.enc_keys[l + 4];
self.dec_keys[j + 5] = self.enc_keys[l + 5];
}
}
fn crypt(&self, mut block: InOut<'_, '_, Block<Self>>, sub_keys: &[u16; LENGTH_SUB_KEYS]) {
let b = block.get_in();
let mut x1 = u16::from_be_bytes(b[0..2].try_into().unwrap());
let mut x2 = u16::from_be_bytes(b[2..4].try_into().unwrap());
let mut x3 = u16::from_be_bytes(b[4..6].try_into().unwrap());
let mut x4 = u16::from_be_bytes(b[6..8].try_into().unwrap());
for i in 0..ROUNDS {
let j = i * 6;
let y1 = self.mul(x1, sub_keys[j]);
let y2 = self.add(x2, sub_keys[j + 1]);
let y3 = self.add(x3, sub_keys[j + 2]);
let y4 = self.mul(x4, sub_keys[j + 3]);
let t0 = self.mul(y1 ^ y3, sub_keys[j + 4]);
let _t = self.add(y2 ^ y4, t0);
let t1 = self.mul(_t, sub_keys[j + 5]);
let t2 = self.add(t0, t1);
x1 = y1 ^ t1;
x2 = y3 ^ t1;
x3 = y2 ^ t2;
x4 = y4 ^ t2;
}
let y1 = self.mul(x1, sub_keys[48]);
let y2 = self.add(x3, sub_keys[49]);
let y3 = self.add(x2, sub_keys[50]);
let y4 = self.mul(x4, sub_keys[51]);
let block = block.get_out();
block[0..2].copy_from_slice(&y1.to_be_bytes());
block[2..4].copy_from_slice(&y2.to_be_bytes());
block[4..6].copy_from_slice(&y3.to_be_bytes());
block[6..8].copy_from_slice(&y4.to_be_bytes());
}
fn mul(&self, a: u16, b: u16) -> u16 {
let x = u32::from(a);
let y = u32::from(b);
let mut r: i32;
if x == 0 {
r = (MAXIM - y) as i32;
} else if y == 0 {
r = (MAXIM - x) as i32;
} else {
let c: u32 = x * y;
r = ((c & ONE) as i32) - ((c >> 16) as i32);
if r < 0 {
r += MAXIM as i32;
}
}
(r & (ONE as i32)) as u16
}
fn add(&self, a: u16, b: u16) -> u16 {
((u32::from(a) + u32::from(b)) & ONE) as u16
}
fn mul_inv(&self, a: u16) -> u16 {
if a <= 1 {
a
} else {
let mut x = u32::from(a);
let mut y = MAXIM;
let mut t0 = 1u32;
let mut t1 = 0u32;
loop {
t1 += y / x * t0;
y %= x;
if y == 1 {
return (MAXIM - t1) as u16;
}
t0 += x / y * t1;
x %= y;
if x == 1 {
return t0 as u16;
}
}
}
}
fn add_inv(&self, a: u16) -> u16 {
((FUYI - (u32::from(a))) & ONE) as u16
}
}
impl BlockCipher for Idea {}
impl KeySizeUser for Idea {
type KeySize = U16;
}
impl KeyInit for Idea {
fn new(key: &Key<Self>) -> Self {
let mut cipher = Self {
enc_keys: [0u16; 52],
dec_keys: [0u16; 52],
};
cipher.expand_key(key);
cipher.invert_sub_keys();
cipher
}
}
impl fmt::Debug for Idea {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str("Idea { ... }")
}
}
impl AlgorithmName for Idea {
fn write_alg_name(f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.write_str("Idea")
}
}
#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl Drop for Idea {
fn drop(&mut self) {
self.enc_keys.zeroize();
self.dec_keys.zeroize();
}
}
#[cfg(feature = "zeroize")]
#[cfg_attr(docsrs, doc(cfg(feature = "zeroize")))]
impl ZeroizeOnDrop for Idea {}
cipher::impl_simple_block_encdec!(
Idea, U8, cipher, block,
encrypt: {
cipher.crypt(block, &cipher.enc_keys);
}
decrypt: {
cipher.crypt(block, &cipher.dec_keys);
}
);