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const DELTA: u32 = 0x9E3779B9;

fn to_bytes(v: &Vec<u32>, include_length: bool) -> Vec<u8> {
    let length: u32 = v.len() as u32;
    let mut n: u32 = length << 2;
    if include_length {
        let m: u32 = v[length as usize - 1];
        n = n - 4;
        assert!(!((m < n - 3) || (m > n)));
        n = m;
    }
    let mut bytes: Vec<u8> = vec![0; n as usize];
    for i in 0..n {
        bytes[i as usize] = (v[(i >> 2) as usize] >> ((i & 3) << 3)) as u8;
    }
    return bytes;
}


fn to_u32(bytes: &Vec<u8>, include_length: bool) -> Vec<u32> {
    let length: u32 = bytes.len() as u32;
    let mut n: u32 = length >> 2;
    if length & 3 != 0 {
        n = n + 1;
    }
    let mut v;
    if include_length {
        v = vec![0; n as usize + 1];
        v[n as usize] = length;
    } else {
        v = vec![0; n as usize];
    }
    for i in 0..length {
        v[(i >> 2) as usize] |= (bytes[i as usize] as u32) << ((i & 3) << 3) as u32;
    }
    return v;
}

fn mx(sum: u32, y: u32, z: u32, p: u32, e: u32, k: &Vec<u32>) -> u32 {
    ((z >> 5 ^ y << 2).wrapping_add(y >> 3 ^ z << 4)) ^ ((sum ^ y).wrapping_add(k[(p & 3 ^ e) as usize] ^ z))
}

fn fixk(k: &Vec<u32>) -> Vec<u32> {
    let mut key = k.clone();
    if key.len() < 4 {
        let length = key.len();
        for _ in length..4 {
            key.push(0)
        }
    }
    key
}

fn encrypt_(v: &mut Vec<u32>, k: &Vec<u32>) -> Vec<u32> {
    let length: u32 = v.len() as u32;
    let n: u32 = length - 1;
    let key: Vec<u32> = fixk(k);
    let mut e: u32;
    let mut y: u32;
    let mut z = v[n as usize];
    let mut sum: u32 = 0;
    let mut q: u32 = 6 + 52 / length;
    while q > 0 {
        sum = sum.wrapping_add(DELTA);
        e = sum >> 2 & 3;
        for p in 0..n {
            y = v[(p as usize) +1];
            v[p as usize] = v[p as usize].wrapping_add(mx(sum, y, z, (p as u32), e, &key));
            z = v[p as usize];
        }
        y = v[0];
        v[n as usize] = v[n as usize].wrapping_add(mx(sum, y, z, n, e, &key));
        z = v[n as usize];
        q = q - 1;
    }
    return v.clone();
}

fn decrypt_(v: &mut Vec<u32>, k: &Vec<u32>) -> Vec<u32>{
        let length: u32 = v.len() as u32;
        let n: u32 = length - 1;
        let key: Vec<u32> = fixk(k);
        let mut e: u32;
        let mut y: u32 = v[0];
        let mut z;
        let q: u32 = 6 + 52 / length;
        let mut sum: u32 = q.wrapping_mul(DELTA);
        while sum != 0 {
            e = sum >> 2 & 3;
            let mut p:usize = n as usize;
            while p > 0 {
                z = v[p - 1];
                v[p] = v[p].wrapping_sub(mx(sum, y, z, (p as u32), e, &key));
                y = v[p];
                p = p - 1;
            }
            z = v[n as usize];
            v[0] = v[0].wrapping_sub(mx(sum, y, z, 0, e, &key));
            y = v[0];
            sum = sum.wrapping_sub(DELTA);
        }
        return v.clone();
}

pub fn encrypt(data: &str, key: &str) -> Vec<u8> {
    let data = data.bytes().collect();
    let key = key.bytes().collect();
    to_bytes(&encrypt_(&mut to_u32(&data, true), &to_u32(&key, false)),
            false)
}

pub fn decrypt(data: &Vec<u8>, key: &str) -> Vec<u8> {
    let key = key.bytes().collect();
    to_bytes(&decrypt_(&mut to_u32(&data, false), &to_u32(&key, false)),
            true)
}

/// Encrypt a u8 vector with XXTEA
///
/// *Note:* XXTEA works on 32 bit words. If input is not evenly dividable by
/// four, it will be padded with zeroes. Padding information is lost after the
/// encryption and this needs to be taken into consideration when decrypting
/// messages.
///
/// # Arguments
///
/// * `data` - The data to be encrypted
/// * `key` - encryption key
///
/// # Example
///
/// ```
/// let key : &str = "SecretKey";
/// let data : [u8; 5] = [11, 13, 0, 14, 15];
///
/// let encrypted_data = xxtea::encrypt_raw(&data.to_vec(), &key);
/// // encrypted data will be 8 bytes (3 zeroes appended to the end)
/// println!("Encrypted data: {:?}", encrypted_data);
/// ```
///
pub fn encrypt_raw(data: &Vec<u8>, key: &str) -> Vec<u8> {
    let key = key.bytes().collect();
    to_bytes(&encrypt_(&mut to_u32(&data, false), &to_u32(&key, false)),
            false)
}

/// Decrypt a u8 vector with XXTEA
///
/// The output isn't verified for correctness, thus additional checks needs to
/// be performed on the output.
///
/// # Arguments
///
/// * `data` - The data to be decrypted
/// * `key` - encryption key
///
/// # Example
///
/// ```
/// let key : &str = "SecretKey";
/// let data : [u8; 5] = [11, 13, 0, 14, 15];
///
/// let decrypted_data = xxtea::decrypt_raw(&data.to_vec(), &key);
/// println!("Decrypted data: {:?}", decrypted_data);
/// ```
///
pub fn decrypt_raw(data: &Vec<u8>, key: &str) -> Vec<u8> {
    let key = key.bytes().collect();
    to_bytes(&decrypt_(&mut to_u32(&data, false), &to_u32(&key, false)),
            false)
}