solve Challenge 5 of Set 1

Cargo.lock

@@ -149,6 +149,16 @@ version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c08c74e62047bb2de4ff487b251e4a92e24f48745648451635cec7d591162d9f"
 
+[[package]]
+name = "repeating_xor"
+version = "0.1.0"
+dependencies = [
+ "common",
+ "env_logger",
+ "log",
+ "rustc-serialize",
+]
+
 [[package]]
 name = "rustc-serialize"
 version = "0.3.25"

Cargo.toml

@@ -6,5 +6,6 @@ members = [
   "set1/challenge2_fixed_xor",
   "set1/challenge3_xor_cipher",
   "set1/challenge4_detect_xor",
+  "set1/challenge5_repeating_xor",
 ]
 resolver = "2"

common/src/lib.rs

@@ -18,15 +18,19 @@ pub fn score(plaintext: &Vec<u8>) -> u32 {
     score
 }
 
-pub fn fixed_xor_cipher(ciphertext: &Vec<u8>, keyiter: &mut dyn Iterator<Item = u8>) -> Vec<u8> {
-    ciphertext.iter().zip(keyiter).map(|(c, k)| c ^ k).collect()
+pub fn generic_xor_cipher(text: &[u8], keyiter: &mut dyn Iterator<Item = &u8>) -> Vec<u8> {
+    text.iter().zip(keyiter).map(|(c, k)| c ^ k).collect()
 }
 
-pub fn xor_cipher(ciphertext: &Vec<u8>, key: u8) -> Vec<u8> {
-    fixed_xor_cipher(ciphertext, &mut repeat(key))
+pub fn fixed_xor_cipher(text: &[u8], key: &[u8]) -> Vec<u8> {
+    generic_xor_cipher(text, &mut key.iter())
 }
 
-pub fn break_xor_cipher(ciphertext: &Vec<u8>) -> (Vec<u8>, u32) {
+pub fn xor_cipher(text: &[u8], key: u8) -> Vec<u8> {
+    generic_xor_cipher(text, &mut repeat(&key))
+}
+
+pub fn break_xor_cipher(ciphertext: &[u8]) -> (Vec<u8>, u32) {
     let mut maxscore = 0;
     let mut decrypted: Vec<u8> = vec![];
 
@@ -40,3 +44,7 @@ pub fn break_xor_cipher(ciphertext: &Vec<u8>) -> (Vec<u8>, u32) {
     }
     (decrypted, maxscore)
 }
+
+pub fn repeating_xor_cipher(text: &[u8], key: &[u8]) -> Vec<u8> {
+    generic_xor_cipher(text, &mut key.iter().cycle())
+}

set1/challenge2_fixed_xor/src/main.rs

@@ -22,7 +22,7 @@ fn main() {
 
     for (line1, line2) in Pairwise(stdin().lock().lines().filter_map(|x| x.ok())) {
         match (line1.from_hex(), line2.from_hex()) {
-            (Ok(v1), Ok(v2)) => println!("{}", fixed_xor_cipher(&v1, &mut v2.into_iter()).to_hex()),
+            (Ok(v1), Ok(v2)) => println!("{}", fixed_xor_cipher(v1.as_slice(), v2.as_slice()).to_hex()),
             (Err(e), _) => error!("{}", e),
             (_, Err(e)) => error!("{}", e)
         }
@@ -37,7 +37,7 @@ mod tests {
     fn challenge2_fixed_xor() {
         let v1 = "1c0111001f010100061a024b53535009181c".from_hex().unwrap();
         let v2 = "686974207468652062756c6c277320657965".from_hex().unwrap();
-        let r = fixed_xor_cipher(&v1, &mut v2.into_iter()).to_hex();
+        let r = fixed_xor_cipher(v1.as_slice(), v2.as_slice()).to_hex();
         assert_eq!(r, "746865206b696420646f6e277420706c6179");
     }
 }

set1/challenge3_xor_cipher/src/main.rs

@@ -9,7 +9,7 @@ fn main() {
     for line in stdin().lock().lines().filter_map(|x| x.ok()) {
         match line.from_hex() {
             Ok(ciphertext) => {
-                let (decrypted, _) = break_xor_cipher(&ciphertext);
+                let (decrypted, _) = break_xor_cipher(ciphertext.as_slice());
                 match String::from_utf8(decrypted) {
                     Ok(s) => println!("{}", s),
                     Err(e) => error!("{}", e)
@@ -27,7 +27,7 @@ mod tests {
     #[test]
     fn challenge3_xor_cipher() {
         let ciphertext = "1b37373331363f78151b7f2b783431333d78397828372d363c78373e783a393b3736".from_hex().unwrap();
-        let (decrypted, _) = break_xor_cipher(&ciphertext);
+        let (decrypted, _) = break_xor_cipher(ciphertext.as_slice());
         assert_eq!(String::from_utf8(decrypted).unwrap(), "Cooking MC's like a pound of bacon");
     }
 }

set1/challenge4_detect_xor/src/main.rs

@@ -10,7 +10,7 @@ fn detect_xor(input: &mut dyn BufRead) -> Result<String, Box<dyn Error>> {
 
     for line in input.lines() {
         let ciphertext = line?.from_hex()?;
-        let (plaintext, score) = break_xor_cipher(&ciphertext);
+        let (plaintext, score) = break_xor_cipher(ciphertext.as_slice());
         if score > maxscore {
             maxscore = score;
             decrypted = plaintext;

set1/challenge5_repeating_xor/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "repeating_xor"
+version = "0.1.0"
+edition = "2021"
+authors = ["Thomas Lindner <tom@dl6tom.de>"]
+
+[dependencies]
+common = { path = "../../common" }
+log = "0.4"
+env_logger = "0.10"
+rustc-serialize = "0.3"

set1/challenge5_repeating_xor/src/main.rs

@@ -0,0 +1,24 @@
+use common::repeating_xor_cipher;
+use rustc_serialize::hex::ToHex;
+use std::io::{BufRead, stdin};
+
+fn main() {
+    env_logger::init();
+
+    for line in stdin().lock().lines().filter_map(|x| x.ok()) {
+        let ciphertext = repeating_xor_cipher(line.as_bytes(), "ICE".as_bytes());
+        println!("{}", ciphertext.to_hex());
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn challenge5_repeating_xor() {
+        let plaintext = "Burning 'em, if you ain't quick and nimble\nI go crazy when I hear a cymbal".as_bytes();
+        let ciphertext = repeating_xor_cipher(plaintext, "ICE".as_bytes());
+        assert_eq!(ciphertext.to_hex(), "0b3637272a2b2e63622c2e69692a23693a2a3c6324202d623d63343c2a26226324272765272a282b2f20430a652e2c652a3124333a653e2b2027630c692b20283165286326302e27282f");
+    }
+}