Main program for a secured client-srver communication.

encryption.py

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+import os
+
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes
+from cryptography.hazmat.primitives import padding
+
+
+key = os.urandom(16)
+
+# iv = os.urandom(16)
+# iv_2 = os.urandom(16)
+
+iv_1 = b'\x00' * 16
+iv_2 = b'\x00' * 16
+
+cipher = Cipher(algorithms.AES(key), modes.CBC(iv_1))
+print(f"block size AES: {algorithms.AES.block_size}")
+
+encryptor = cipher.encryptor()
+ciphertext = encryptor.update(b"a secret message") + encryptor.finalize()
+print(f"ciphertext={ciphertext!r}")
+print(f"len(ciphertext)={len(ciphertext)}")
+
+cipher_2 = Cipher(algorithms.AES(key), modes.CBC(iv_2))
+decryptor = cipher_2.decryptor()
+
+res = decryptor.update(ciphertext) + decryptor.finalize()
+print(f"res={res!r}")