68 lines
2.3 KiB
Rust
68 lines
2.3 KiB
Rust
use cryptopals::{prelude::*, bvec, bvec64, english::{Bhattacharyya, self}};
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fn main() {
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let s1 = b"this is a test".to_vec();
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let s2 = b"wokka wokka!!!".to_vec();
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assert_eq!(s1.hamming(&s2).unwrap(), 37);
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// infer key size
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let input = bvec64!("input.txt");
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let mut keysizes = (2..=40).map(|possible_keysize| {
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let pk=possible_keysize;
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let bl0 = input[0*pk..1*pk].to_vec();
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let bl1 = input[1*pk..2*pk].to_vec();
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let bl2 = input[2*pk..3*pk].to_vec();
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let bl3 = input[3*pk..4*pk].to_vec();
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let bl4 = input[4*pk..5*pk].to_vec();
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let score = (
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bl0.hamming(&bl1).unwrap() +
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bl1.hamming(&bl2).unwrap() +
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bl2.hamming(&bl3).unwrap() +
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bl3.hamming(&bl4).unwrap()
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) * 100000 / (4 * pk as u64) ;
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(pk, score)
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}).collect::<Vec<_>>();
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keysizes.sort_by_key(|(_, score)| *score);
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keysizes.drain(4..);
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dbg!(&keysizes);
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// use bhattacharyya distance to guess each key
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let sample = include_bytes!("sample.txt");
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let ideal_distribution = Bhattacharyya::compute(sample);
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let possible_keys: Vec<Vec<u8>> = keysizes.iter().map(|(keysize, _)| {
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let key = (0..*keysize).map(|key_i| {
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let mut ciphertext_chunk=vec![];
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for i in (key_i..input.len()).step_by(*keysize) {
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ciphertext_chunk.push(input[i]);
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}
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let mut possible_bytes = (u8::MIN..=u8::MAX).map(|key_byte| {
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let plaintext = ciphertext_chunk.xor_repeating(&vec![key_byte]).unwrap();
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let score = Bhattacharyya::compute(&plaintext).score(&ideal_distribution);
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(key_byte, (score * 100000.0) as i32)
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}).collect::<Vec<_>>();
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possible_bytes.sort_by_key(|(_, sc)| -sc);
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possible_bytes.drain(1..);
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possible_bytes[0].0 // TODO: Use multiple possibilities
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}).collect::<Vec<_>>();
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key
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}).collect::<Vec<_>>();
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let mut outcomes = possible_keys.iter().map(|key| {
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let output = input.xor_repeating(&key).unwrap();
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let score = english::score(&output);
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(key, output, score)
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}).collect::<Vec<_>>();
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outcomes.sort_by_key(|(_, _, sc)| -sc);
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dbg!(outcomes[0].0.to_hex());
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dbg!(outcomes[0].1.to_text().unwrap());
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println!("pass!")
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} |