finished hw

part1/alice.py

@@ -0,0 +1,33 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import pad
+from Crypto.Random import get_random_bytes
+
+
+# Generate new secret key
+with open('key', 'wb') as f:
+    k1 = get_random_bytes(16)
+    f.write(k1)
+
+plaintext = input("Please input the message: ")
+
+# Pad plaintext
+plaintext = plaintext.encode()
+
+plaintext = pad(plaintext, 16)
+
+# Read Key
+with open('key', 'rb') as f:
+    aes_key = f.read()
+
+assert k1 == aes_key
+
+# Encrypt and send (write) message
+cipher = AES.new(aes_key, AES.MODE_CBC, iv=b'0'*16)
+
+ciphertext = cipher.encrypt(plaintext)
+
+with open('ctext', 'wb') as f:
+    f.write(ciphertext)
+
+
+

part1/bob.py

@@ -0,0 +1,18 @@
+from Crypto.Cipher import AES
+from Crypto.Util.Padding import unpad
+
+# Read Key
+with open('key', 'rb') as f:
+    aes_key = f.read()
+
+cipher = AES.new(aes_key, AES.MODE_CBC, iv=b'0'*16)
+
+# Read message and decrypt
+
+with open('ctext', 'rb') as f:
+    ciphertext = f.read()
+
+plaintext = unpad(cipher.decrypt(ciphertext), 16).decode()
+
+print(f'Plaintext: {plaintext}')
+