static SBOX: [u8; 256] = [
0xd6, 0x90, 0xe9, 0xfe, 0xcc, 0xe1, 0x3d, 0xb7, 0x16, 0xb6, 0x14, 0xc2, 0x28, 0xfb, 0x2c, 0x05,
0x2b, 0x67, 0x9a, 0x76, 0x2a, 0xbe, 0x04, 0xc3, 0xaa, 0x44, 0x13, 0x26, 0x49, 0x86, 0x06, 0x99,
0x9c, 0x42, 0x50, 0xf4, 0x91, 0xef, 0x98, 0x7a, 0x33, 0x54, 0x0b, 0x43, 0xed, 0xcf, 0xac, 0x62,
0xe4, 0xb3, 0x1c, 0xa9, 0xc9, 0x08, 0xe8, 0x95, 0x80, 0xdf, 0x94, 0xfa, 0x75, 0x8f, 0x3f, 0xa6,
0x47, 0x07, 0xa7, 0xfc, 0xf3, 0x73, 0x17, 0xba, 0x83, 0x59, 0x3c, 0x19, 0xe6, 0x85, 0x4f, 0xa8,
0x68, 0x6b, 0x81, 0xb2, 0x71, 0x64, 0xda, 0x8b, 0xf8, 0xeb, 0x0f, 0x4b, 0x70, 0x56, 0x9d, 0x35,
0x1e, 0x24, 0x0e, 0x5e, 0x63, 0x58, 0xd1, 0xa2, 0x25, 0x22, 0x7c, 0x3b, 0x01, 0x21, 0x78, 0x87,
0xd4, 0x00, 0x46, 0x57, 0x9f, 0xd3, 0x27, 0x52, 0x4c, 0x36, 0x02, 0xe7, 0xa0, 0xc4, 0xc8, 0x9e,
0xea, 0xbf, 0x8a, 0xd2, 0x40, 0xc7, 0x38, 0xb5, 0xa3, 0xf7, 0xf2, 0xce, 0xf9, 0x61, 0x15, 0xa1,
0xe0, 0xae, 0x5d, 0xa4, 0x9b, 0x34, 0x1a, 0x55, 0xad, 0x93, 0x32, 0x30, 0xf5, 0x8c, 0xb1, 0xe3,
0x1d, 0xf6, 0xe2, 0x2e, 0x82, 0x66, 0xca, 0x60, 0xc0, 0x29, 0x23, 0xab, 0x0d, 0x53, 0x4e, 0x6f,
0xd5, 0xdb, 0x37, 0x45, 0xde, 0xfd, 0x8e, 0x2f, 0x03, 0xff, 0x6a, 0x72, 0x6d, 0x6c, 0x5b, 0x51,
0x8d, 0x1b, 0xaf, 0x92, 0xbb, 0xdd, 0xbc, 0x7f, 0x11, 0xd9, 0x5c, 0x41, 0x1f, 0x10, 0x5a, 0xd8,
0x0a, 0xc1, 0x31, 0x88, 0xa5, 0xcd, 0x7b, 0xbd, 0x2d, 0x74, 0xd0, 0x12, 0xb8, 0xe5, 0xb4, 0xb0,
0x89, 0x69, 0x97, 0x4a, 0x0c, 0x96, 0x77, 0x7e, 0x65, 0xb9, 0xf1, 0x09, 0xc5, 0x6e, 0xc6, 0x84,
0x18, 0xf0, 0x7d, 0xec, 0x3a, 0xdc, 0x4d, 0x20, 0x79, 0xee, 0x5f, 0x3e, 0xd7, 0xcb, 0x39, 0x48,
];
fn split(input: u32) -> [u8; 4] {
let i4: u8 = (input & 0xff) as u8;
let i3: u8 = ((input >> 8) & 0xff) as u8;
let i2: u8 = ((input >> 16) & 0xff) as u8;
let i1: u8 = ((input >> 24) & 0xff) as u8;
[i1, i2, i3, i4]
}
fn combine(input: &[u8]) -> u32 {
let out: u32 = u32::from(input[3]);
let out = out + (u32::from(input[2]) << 8);
let out = out + (u32::from(input[1]) << 16);
out + (u32::from(input[0]) << 24)
}
fn split_block(input: &[u8]) -> [u32; 4] {
if input.len() != 16 {
panic!("the block size of SM4 must be 16.")
}
let mut out: [u32; 4] = [0; 4];
for (i, v) in out.iter_mut().enumerate().take(4) {
let start = 4 * i;
let end = 4 * i + 4;
*v = combine(&input[start..end])
}
out
}
fn combine_block(input: &[u32]) -> [u8; 16] {
let mut out: [u8; 16] = [0; 16];
for i in 0..4 {
let outi = split(input[i]);
for j in 0..4 {
out[i * 4 + j] = outi[j];
}
}
out
}
fn tau_trans(input: u32) -> u32 {
let input = split(input);
let mut out: [u8; 4] = [0; 4];
for i in 0..4 {
out[i] = SBOX[input[i] as usize];
}
combine(&out)
}
fn l_rotate(x: u32, i: u32) -> u32 {
(x << (i % 32)) | (x >> (32 - (i % 32)))
}
fn l_trans(input: u32) -> u32 {
let b = input;
b ^ l_rotate(b, 2) ^ l_rotate(b, 10) ^ l_rotate(b, 18) ^ l_rotate(b, 24)
}
fn t_trans(input: u32) -> u32 {
l_trans(tau_trans(input))
}
fn l_prime_trans(input: u32) -> u32 {
let b = input;
b ^ l_rotate(b, 13) ^ l_rotate(b, 23)
}
fn t_prime_trans(input: u32) -> u32 {
l_prime_trans(tau_trans(input))
}
pub struct Sm4Cipher {
rk: Vec<u32>,
}
static FK: [u32; 4] = [0xa3b1_bac6, 0x56aa_3350, 0x677d_9197, 0xb270_22dc];
static CK: [u32; 32] = [
0x0007_0e15,
0x1c23_2a31,
0x383f_464d,
0x545b_6269,
0x7077_7e85,
0x8c93_9aa1,
0xa8af_b6bd,
0xc4cb_d2d9,
0xe0e7_eef5,
0xfc03_0a11,
0x181f_262d,
0x343b_4249,
0x5057_5e65,
0x6c73_7a81,
0x888f_969d,
0xa4ab_b2b9,
0xc0c7_ced5,
0xdce3_eaf1,
0xf8ff_060d,
0x141b_2229,
0x3037_3e45,
0x4c53_5a61,
0x686f_767d,
0x848b_9299,
0xa0a7_aeb5,
0xbcc3_cad1,
0xd8df_e6ed,
0xf4fb_0209,
0x1017_1e25,
0x2c33_3a41,
0x484f_565d,
0x646b_7279,
];
impl Sm4Cipher {
pub fn new(key: &[u8]) -> Sm4Cipher {
let mut k: [u32; 4] = split_block(&key);
let mut cipher = Sm4Cipher { rk: Vec::new() };
for i in 0..4 {
k[i] ^= FK[i];
}
for i in 0..8 {
k[0] ^= t_prime_trans(k[1] ^ k[2] ^ k[3] ^ CK[i * 4]);
k[1] ^= t_prime_trans(k[2] ^ k[3] ^ k[0] ^ CK[i * 4 + 1]);
k[2] ^= t_prime_trans(k[3] ^ k[0] ^ k[1] ^ CK[i * 4 + 2]);
k[3] ^= t_prime_trans(k[0] ^ k[1] ^ k[2] ^ CK[i * 4 + 3]);
cipher.rk.push(k[0]);
cipher.rk.push(k[1]);
cipher.rk.push(k[2]);
cipher.rk.push(k[3]);
}
cipher
}
pub fn encrypt(&self, block_in: &[u8]) -> [u8; 16] {
let mut x: [u32; 4] = split_block(block_in);
let rk = &self.rk;
for i in 0..8 {
x[0] ^= t_trans(x[1] ^ x[2] ^ x[3] ^ rk[i * 4]);
x[1] ^= t_trans(x[2] ^ x[3] ^ x[0] ^ rk[i * 4 + 1]);
x[2] ^= t_trans(x[3] ^ x[0] ^ x[1] ^ rk[i * 4 + 2]);
x[3] ^= t_trans(x[0] ^ x[1] ^ x[2] ^ rk[i * 4 + 3]);
}
let y = [x[3], x[2], x[1], x[0]];
combine_block(&y)
}
pub fn decrypt(&self, block_in: &[u8]) -> [u8; 16] {
let mut x: [u32; 4] = split_block(block_in);
let rk = &self.rk;
for i in 0..8 {
x[0] ^= t_trans(x[1] ^ x[2] ^ x[3] ^ rk[31 - i * 4]);
x[1] ^= t_trans(x[2] ^ x[3] ^ x[0] ^ rk[31 - (i * 4 + 1)]);
x[2] ^= t_trans(x[3] ^ x[0] ^ x[1] ^ rk[31 - (i * 4 + 2)]);
x[3] ^= t_trans(x[0] ^ x[1] ^ x[2] ^ rk[31 - (i * 4 + 3)]);
}
let y = [x[3], x[2], x[1], x[0]];
combine_block(&y)
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn setup_cipher() {
let key: [u8; 16] = [
0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54,
0x32, 0x10,
];
let cipher = Sm4Cipher::new(&key);
let rk = &cipher.rk;
assert_eq!(rk[0], 0xf121_86f9);
assert_eq!(rk[31], 0x9124_a012);
}
#[test]
fn enc_and_dec() {
let key: [u8; 16] = [
0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54,
0x32, 0x10,
];
let cipher = Sm4Cipher::new(&key);
let data: [u8; 16] = [
0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0xfe, 0xdc, 0xba, 0x98, 0x76, 0x54,
0x32, 0x10,
];
let ct = cipher.encrypt(&data);
let standard_ct: [u8; 16] = [
0x68, 0x1e, 0xdf, 0x34, 0xd2, 0x06, 0x96, 0x5e, 0x86, 0xb3, 0xe9, 0x4f, 0x53, 0x6e,
0x42, 0x46,
];
for i in 0..16 {
assert_eq!(standard_ct[i], ct[i]);
}
let pt = cipher.decrypt(&ct);
for i in 0..16 {
assert_eq!(pt[i], data[i]);
}
}
}