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xor_decryption.rs
35 lines (33 loc) · 1.04 KB
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xor_decryption.rs
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pub fn solve() -> i64 {
let cipher_bytes = std::fs::read_to_string("res/solutions/xor_decryption.txt")
.unwrap()
.split(',')
.map(|s| s.parse().unwrap())
.collect::<Vec<u8>>();
let mut key_bytes = [b'a', b'a', b'a'];
let sum = loop {
let plain_bytes = cipher_bytes
.iter()
.zip(key_bytes.iter().cycle())
.map(|(cipher_byte, key_byte)| cipher_byte ^ key_byte)
.collect::<Vec<u8>>();
let plaintext = std::str::from_utf8(&plain_bytes).unwrap();
if plaintext.contains(" the ") {
break plain_bytes.iter().fold(0i64, |sum, &byte| sum + byte as i64);
}
// Set up the next key.
if key_bytes[2] != b'z' {
key_bytes[2] += 1;
} else {
key_bytes[2] = b'a';
if key_bytes[1] != b'z' {
key_bytes[1] += 1;
} else {
key_bytes[1] = b'a';
key_bytes[0] += 1;
}
}
};
assert_eq!(sum, 129448);
sum
}