From 0c3876f9f5a6c6c0e9aabe494c04d614b8f647e1 Mon Sep 17 00:00:00 2001
From: Sam Hadow <sam.hadow@proton.me>
Date: Tue, 7 Apr 2026 09:18:55 +0200
Subject: [PATCH] test non linearity

---
 src/tea3.rs | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/src/tea3.rs b/src/tea3.rs
index b347c9b..633111a 100644
--- a/src/tea3.rs
+++ b/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());
+    }
 }