Idiomatic Rust Snippets

AES Algorithm (WIP)

AES (Advanced Encryption Standard) is a symmetric encryption algorithm widely used across the globe. Below is a simple implementation of the AES algorithm in Rust without using any existing libraries.

const S_BOX: [u8; 256] = [
    // S-Box values here...
];

fn sub_bytes(state: &mut [u8; 16]) {
    for i in 0..16 {
        state[i] = S_BOX[state[i] as usize];
    }
}

fn shift_rows(state: &mut [u8; 16]) {
    let mut temp = [0u8; 16];
    for i in 0..16 {
        temp[i] = state[i];
    }
    for i in 0..4 {
        for j in 0..4 {
            state[i + 4 * j] = temp[i + 4 * ((j + i) % 4)];
        }
    }
}

fn mix_columns(state: &mut [u8; 16]) {
    // MixColumns implementation here...
}

fn add_round_key(state: &mut [u8; 16], round_key: &[u8; 16]) {
    for i in 0..16 {
        state[i] ^= round_key[i];
    }
}

fn aes_encrypt_block(block: &mut [u8; 16], key: &[u8; 16]) {
    let mut round_keys = [0u8; 176];
    key_expansion(key, &mut round_keys);

    add_round_key(block, &round_keys[0..16]);

    for round in 1..10 {
        sub_bytes(block);
        shift_rows(block);
        mix_columns(block);
        add_round_key(block, &round_keys[round * 16..(round + 1) * 16]);
    }

    sub_bytes(block);
    shift_rows(block);
    add_round_key(block, &round_keys[160..176]);
}

fn key_expansion(key: &[u8; 16], round_keys: &mut [u8; 176]) {
    // Key expansion implementation here...
}

fn main() {
    let mut block = [0x32, 0x43, 0xf6, 0xa8, 0x88, 0x5a, 0x30, 0x8d, 0x31, 0x31, 0x98, 0xa2, 0xe0, 0x37, 0x07, 0x34];
    let key = [0x2b, 0x7e, 0x15, 0x16, 0x28, 0xae, 0xd2, 0xa6, 0xab, 0xf7, 0x4d, 0x4a, 0x4e, 0xa6, 0x2b, 0x7e];

    aes_encrypt_block(&mut block, &key);

    println!("Encrypted block: {:?}", block);
}

This example provides a basic structure for AES encryption. Note that the S_BOX, mix_columns, and key_expansion functions need to be fully implemented for a complete AES encryption algorithm.

1. SubBytes: This step substitutes each byte in the state with a corresponding byte from the S-Box.
2. ShiftRows: This step shifts the rows of the state array cyclically.
3. MixColumns: This step mixes the columns of the state array.
4. AddRoundKey: This step adds (XORs) the round key to the state.
5. KeyExpansion: This step generates round keys from the initial key.

The aes_encrypt_block function performs the encryption by applying these steps in the correct order for 10 rounds.

This is a simplified version and does not include all the details required for a secure AES implementation. For production use, consider using a well-tested cryptographic library.