eryn/cryptopals
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Now it actually works...

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This commit is contained in:
Eryn Wells 2018-04-05 07:19:29 -07:00
parent be04722ce7
commit fb457ac1ab
1 changed files with 16 additions and 7 deletions
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23
src/xor.rs
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@ -1,3 +1,4 @@
use std::f32;
use std::iter;
pub type FixedXOR<T, U> = iter::Map<iter::Zip<T, U>, fn((u8, u8)) -> u8>;
@ -57,16 +58,22 @@ mod tests {
let mut freqs: Vec<f32> = iter::repeat(0.0f32).take(26).collect();
let mut num_alphabetic_chars = 0f32;
for c in input.chars() {
if !c.is_ascii_alphabetic() {
continue;
}
num_alphabetic_chars += 1f32;
if !c.is_alphabetic() { continue; }
let c = c.to_ascii_uppercase();
freqs[c as usize - 'A' as usize] += 1f32;
println!("char:{} freqs:{:?}", c, freqs);
}
let freqs = freqs.into_iter().map(|sc| sc / num_alphabetic_chars);
println!("freqs:{:?}", freqs);
// Calculate chi-squared for this string, comparing actual frequencies vs. English letter
// frequencies.
let score = freqs.zip(ENGLISH_LETTER_FREQS.iter())
.fold(0f32, |acc, (obs, exp)| acc + (obs - exp).powf(2.0) / exp);
let expected_freqs = ENGLISH_LETTER_FREQS.iter().map(|x| x * num_alphabetic_chars);
let score = freqs.into_iter()
.zip(expected_freqs.into_iter())
.inspect(|&(obs, exp)| println!("obs:{}, exp:{}", obs, exp))
.fold(0f32, |acc, (obs, exp)| acc + ((obs - exp).powf(2.0) / exp));
score
}
@ -74,7 +81,7 @@ mod tests {
fn cryptopals13() {
let input = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736";
let mut best_key = 0u8;
let mut best_score = -1f32;
let mut best_score = f32::INFINITY;
let mut best_output: Option<String> = None;
for key in 32u8..127 {
let possible_output = input.chars().hex_decoded()
@ -82,13 +89,15 @@ mod tests {
.map(|x| char::from(x))
.collect::<String>();
let score = letter_freq_score(&possible_output);
if score > best_score {
println!("{}: {:?} -> {}", key, possible_output, score);
if !score.is_nan() && score < best_score {
best_score = score;
best_output = Some(possible_output);
best_key = key;
}
}
let best_output = best_output.expect("expected output");
println!("{}: {} -> {}", best_key, best_output, best_score);
println!("{}: {:?} -> {}", best_key, best_output, best_score);
assert!(best_output.to_lowercase().contains("bacon"));
}
}