Fix embarrassing naming error and still don't know what I am doing wrong.

src/main.rs

@@ -1,6 +1,6 @@
 mod bytes;
 mod bytes_base64;
-mod cbs;
+mod cbc;
 mod ecb;
 mod set1;
 mod set2;
@@ -13,7 +13,7 @@ fn main() {
     // set1::challenge5();
     // set1::challenge6();
     // set1::challenge7();
-    // set1::challenge8();
+    set1::challenge8();
     set2::challenge9();
     set2::challenge10();
     set2::challenge11();