Implement challenge 10.

src/set2.rs

@@ -1,4 +1,7 @@
+#![allow(dead_code)]
 use crate::bytes::Bytes;
+use crate::bytes_base64::BytesBase64;
+use crate::cbs;
 
 pub fn challenge9() {
     let mut bytes = Bytes::from_utf8("YELLOW SUBMARINE");
@@ -7,5 +10,26 @@ pub fn challenge9() {
 }
 
 pub fn challenge10() {
-    println!("[TBD] Challenge 10: TBD");
+    fn read(path: &str) -> Bytes {
+        let s = std::fs::read_to_string(path).unwrap();
+        BytesBase64::from_base64(&s).to_bytes()
+    }
+    let iv = Bytes(vec![0; 16]);
+    let key = Bytes::from_utf8("YELLOW SUBMARINE");
+
+    let text = Bytes::from_utf8("aaaabbbbccccddddeeeeffffgggghhhh");
+    let ciphertext = cbs::encrypt(&key, &iv, &text);
+    let roundtrip = cbs::decrypt(&key, &iv, &ciphertext);
+    if text == roundtrip {
+        let ciphertext = read("data/10.txt");
+        let cleartext = cbs::decrypt(&key, &iv, &ciphertext);
+        let output = cleartext.to_utf8()[..10].to_string();
+        println!("[okay] Challenge 10: {}", output);
+    } else {
+        println!("[fail] Challenge 10: rountrip failed");
+    }
+}
+
+pub fn challenge11() {
+    println!("[tbd] Challenge 11: TBD!");
 }