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pub fn fixed_xor (bytes1: &[u8], bytes2: &[u8]) -> Vec<u8> {
return bytes1.iter()
.zip(bytes2.iter())
.map(|(&a, &b)| { a ^ b })
.collect();
}
pub fn repeating_key_xor (plaintext: &[u8], key: &[u8]) -> Vec<u8> {
return fixed_xor(
plaintext,
&key
.iter()
.cycle()
.take(plaintext.len())
.map(|c| *c)
.collect::<Vec<u8>>()[..]
);
}
pub fn hamming (bytes1: &[u8], bytes2: &[u8]) -> u64 {
count_bits(&fixed_xor(bytes1, bytes2)[..])
}
pub fn pad_pkcs7 (block: &[u8], blocksize: u8) -> Vec<u8> {
let padding_bytes = blocksize - (block.len() % blocksize as usize) as u8;
return block
.iter()
.map(|c| *c)
.chain(::std::iter::repeat(padding_bytes).take(padding_bytes as usize))
.collect();
}
pub fn unpad_pkcs7 (block: &[u8]) -> Option<&[u8]> {
let padding_byte = block[block.len() - 1];
let padding_len = padding_byte as usize;
if padding_len > block.len() || padding_len == 0 {
return None;
}
let real_len = block.len() - padding_len;
if block[real_len..].iter().all(|&c| c == padding_byte) {
return Some(&block[..real_len]);
}
else {
return None;
}
}
fn count_bits (bytes: &[u8]) -> u64 {
bytes.iter().map(|&c| { count_bits_byte(c) }).fold(0, |acc, n| acc + n)
}
fn count_bits_byte (byte: u8) -> u64 {
(((byte & (0x01 << 0)) >> 0)
+ ((byte & (0x01 << 1)) >> 1)
+ ((byte & (0x01 << 2)) >> 2)
+ ((byte & (0x01 << 3)) >> 3)
+ ((byte & (0x01 << 4)) >> 4)
+ ((byte & (0x01 << 5)) >> 5)
+ ((byte & (0x01 << 6)) >> 6)
+ ((byte & (0x01 << 7)) >> 7)) as u64
}
#[test]
fn test_hamming () {
assert_eq!(hamming(b"this is a test", b"wokka wokka!!!"), 37);
}
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