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decrypt + test

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Sam Hadow 2024-04-26 18:56:56 +02:00
parent f847cc5b78
commit 7a2a5c567e
1 changed files with 78 additions and 1 deletions
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79
src/aes.rs
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@ -143,7 +143,6 @@ static RC: [u8; 11] = [
0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1B, 0x36,
];
fn clone_into_array<A, T>(slice: &[T]) -> A
where
A: Default + AsMut<[T]>,
@ -273,6 +272,32 @@ fn mix_columns(state: &mut [[u8; 4]; 4]) {
}
}
fn inverse_mix_columns(state: &mut [[u8; 4]; 4]) {
for i in 0..4 {
let mut temp = [0u8; 4];
for j in 0..4 {
temp[j] = state[j][i];
}
state[0][i] = galois_multiplication(temp[0], 14)
^ galois_multiplication(temp[3], 9)
^ galois_multiplication(temp[2], 13)
^ galois_multiplication(temp[1], 11);
state[1][i] = galois_multiplication(temp[1], 14)
^ galois_multiplication(temp[0], 9)
^ galois_multiplication(temp[3], 13)
^ galois_multiplication(temp[2], 11);
state[2][i] = galois_multiplication(temp[2], 14)
^ galois_multiplication(temp[1], 9)
^ galois_multiplication(temp[0], 13)
^ galois_multiplication(temp[3], 11);
state[3][i] = galois_multiplication(temp[3], 14)
^ galois_multiplication(temp[2], 9)
^ galois_multiplication(temp[1], 13)
^ galois_multiplication(temp[0], 11);
}
}
fn add_round_key(state: &mut [[u8; 4]; 4], key: &[[u8; 4]; 4]) {
// for i in 0..4 {
// for j in 0..4 {
@ -333,6 +358,39 @@ impl Aes {
result
}
fn decrypt_block(&self, block: &[u8; 16]) -> [u8; 16] {
let mut result = [0u8; 16];
let mut state = [[0u8; 4]; 4];
for i in 0..16 {
state[i % 4][i / 4] = block[i];
}
add_round_key(&mut state, &clone_into_array(&self.expanded_key[40..44]));
inverse_shift_rows(&mut state);
inverse_substitute_state(&mut state);
for i in (1..self.n_turn).rev() {
add_round_key(
&mut state,
&clone_into_array(&self.expanded_key[i * 4..(i + 1) * 4]),
);
inverse_mix_columns(&mut state);
inverse_shift_rows(&mut state);
inverse_substitute_state(&mut state);
}
add_round_key(&mut state, &clone_into_array(&self.expanded_key[0..4]));
for i in 0..4 {
for j in 0..4 {
result[4 * j + i] = state[i][j]
}
}
result
}
pub fn key_schedule(key_bytes: &[u8; 16]) -> [[u8; 4]; 44] {
let mut original_key = [[0u8; 4]; 4];
let mut expanded_key = [[0u8; 4]; 44];
@ -438,4 +496,23 @@ mod tests {
];
assert_eq!(ciphertext, expected_ciphertext);
}
#[test]
fn decrypt_test() {
let ciphertext: [u8; 16] = [
0x39, 0x25, 0x84, 0x1d, 0x02, 0xdc, 0x09, 0xfb, 0xdc, 0x11, 0x85, 0x97, 0x19, 0x6a,
0x0b, 0x32,
];
let key: [u8; 16] = [
0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x15, 0x88, 0x09, 0xcf,
0x4f, 0x3c,
];
let nturn = 10;
let aescipher = Aes::new(&key, &nturn);
let cleartext: [u8; 16] = aescipher.decrypt_block(&ciphertext);
let expected_cleartext: [u8; 16] = [
0x32, 0x43, 0xf6, 0xa8, 0x88, 0x5a, 0x30, 0x8d, 0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37,
0x07, 0x34,
];
assert_eq!(cleartext, expected_cleartext);
}
}