Detect ECB via duplicated chunks instead of Hemming distance as I should have done in the first place.

src/bytes.rs

@@ -95,6 +95,20 @@ impl Bytes {
         )
     }
 
+    pub fn has_duplicated_cycle(&self, block_size: usize) -> bool {
+        let Bytes(v) = self;
+        let chunks: Vec<&[u8]> = v.chunks(block_size).collect();
+        // we could use a hashmap to get O(n) instead of O(n^2)
+        for i in 0..chunks.len() {
+            for j in (i + 1)..chunks.len() {
+                if chunks[i] == chunks[j] {
+                    return true;
+                }
+            }
+        }
+        false
+    }
+
     #[allow(dead_code)]
     pub fn hemming(Bytes(a): &Bytes, Bytes(b): &Bytes) -> u32 {
         let v: Vec<u32> = Iterator::zip(a.iter(), b.iter())