test non linearity

src/tea3.rs

@@ -394,4 +394,26 @@ mod tests {
 
         assert_eq!(plaintext.to_vec(), decrypted);
     }
+
+    #[test]
+    fn test_non_linearity() {
+        let key = vec![1, 2, 3, 4, 5, 6, 7, 8, 9, 10];
+        let state = vec![0; 8];
+        let mut cipher = Tea3::new(key, state);
+        cipher.init();
+
+        let mut keystream = Vec::with_capacity(72);
+
+        for _ in 0..72 {
+            keystream.push(cipher.next_byte());
+        }
+
+        let poly = Lfsr::berlekamp_massey(&keystream);
+
+
+        let history = &keystream[keystream.len() - (poly.len() - 1)..];
+        let predicted = Lfsr::predict_next_from_poly(history, &poly);
+
+        assert_ne!(predicted, cipher.next_byte());
+    }
 }