finished hw

part2/alice.py

@@ -0,0 +1,20 @@
+from Crypto.PublicKey import RSA
+from Crypto.Cipher import PKCS1_OAEP
+
+# Read Bob's public key
+with open("bob_public.pem", "rb") as f:
+    public_key = RSA.import_key(f.read())
+
+# Get the message from the command line
+message = input("Enter a message: ").encode()
+
+# Create a cipher object using Bob's public key
+cipher = PKCS1_OAEP.new(public_key)
+
+# Encrypt the message
+ciphertext = cipher.encrypt(message)
+
+# Write the ciphertext
+with open("ctext", "wb") as f:
+    f.write(ciphertext)
+

part2/bob.py

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+from Crypto.PublicKey import RSA
+from Crypto.Cipher import PKCS1_OAEP
+import os
+
+# Check if keys already exist
+if not os.path.exists("bob_private.pem"):
+    key = RSA.generate(2048)
+
+    private_key = key.export_key()
+    public_key = key.publickey().export_key()
+
+    # Save the private key
+    with open("bob_private.pem", "wb") as f:
+        f.write(private_key)
+
+    # Save the public key
+    with open("bob_public.pem", "wb") as f:
+        f.write(public_key)
+
+    print("Generated and saved Bob's public and private keys.")
+
+if not os.path.exists('ctext'):
+    print('No ctext found. Run alice.py')
+    exit(0)
+
+# Read the private key
+with open("bob_private.pem", "rb") as f:
+    private_key = RSA.import_key(f.read())
+
+# Read the ciphertext
+with open("ctext", "rb") as f:
+    ciphertext = f.read()
+
+cipher = PKCS1_OAEP.new(private_key)
+
+# Decrypt
+message = cipher.decrypt(ciphertext)
+print("Decrypted message:", message.decode())