Add explicit size assertionf for VALID_KEY and VALID_NONCE

Author: Susmita-Chakrabarty

crypto/tests/test_chacha20.py

@@ -0,0 +1,10 @@
+import random
+import string
+from crypto.ChaCha20 import ChaCha20
+
+VALID_KEY = b"\x00" *32
+assert len(VALID_KEY) == 32, "VALID_KEY must be exactly 32 bytes"
+VALID_NONCE = B"\x00" * 12
+assert len(VALID_NONCE) == 12, "VALID_NONCE must be exactly 12 bytes"
+
+secure_rng = random.SystemRandom()