solve Challenge 3 of Set 1

set1/xor_cipher/Cargo.lock

@@ -0,0 +1,107 @@
+[root]
+name = "xor_cipher"
+version = "0.1.0"
+dependencies = [
+ "env_logger 0.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rustc-serialize 0.3.19 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "aho-corasick"
+version = "0.5.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "memchr 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "env_logger"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 0.1.75 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "kernel32-sys"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "winapi 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "winapi-build 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "libc"
+version = "0.2.16"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "log"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "memchr"
+version = "0.1.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "libc 0.2.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "regex"
+version = "0.1.75"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "aho-corasick 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "thread_local 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "utf8-ranges 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "rustc-serialize"
+version = "0.3.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "thread-id"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.16 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "thread_local"
+version = "0.2.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "thread-id 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "utf8-ranges"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "winapi"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
+name = "winapi-build"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+

set1/xor_cipher/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "xor_cipher"
+version = "0.1.0"
+authors = ["Thomas Lindner <thomas.lindner@fau.de>"]
+
+[dependencies]
+log = "0.3.6"
+env_logger = "0.3.4"
+rustc-serialize = "0.3"

set1/xor_cipher/src/main.rs

@@ -0,0 +1,49 @@
+#[macro_use]
+extern crate log;
+extern crate env_logger;
+extern crate rustc_serialize;
+
+use rustc_serialize::hex::FromHex;
+use std::io::{BufRead, stdin};
+use std::iter::repeat;
+
+fn score(plaintext: &Vec<u8>) -> u32 {
+    let ranking = [24, 7, 15, 17, 26, 11, 10, 19, 22, 4, 5, 16, 13,
+                   21, 23, 8, 2, 18, 20, 25, 14, 6, 12, 3, 9, 1];
+    let mut score = 0;
+
+    for ch in plaintext.iter() {
+        if ch >= &97 && ch <= &122 {
+            score += ranking[(ch - 97) as usize];
+        }
+    }
+    score
+}
+
+fn main() {
+    env_logger::init().unwrap();
+    let stdin = stdin();
+
+    for line in stdin.lock().lines().filter_map(|x| x.ok()) {
+        match line.from_hex() {
+            Ok(ciphertext) => {
+                let mut maxscore = 0;
+                let mut decrypted: Vec<u8> = vec![];
+
+                for key in 0..0xff {
+                    let plaintext: Vec<u8> = ciphertext.iter().zip(repeat(key)).map(|(c, k)| c ^ k).collect();
+                    let s = score(&plaintext);
+                    if s > maxscore {
+                        maxscore = s;
+                        decrypted = plaintext;
+                    }
+                }
+                match String::from_utf8(decrypted) {
+                    Ok(s) => println!("{}", s),
+                    Err(e) => error!("{}", e)
+                }
+            }
+            Err(e) => error!("{}", e)
+        }
+    }
+}