added lab2 q1

IS/Lab/Lab2/des.py

@@ -0,0 +1,36 @@
+from Crypto.Cipher import DES
+
+def des_cipher(key):
+    return DES.new(key.encode('utf-8'), DES.MODE_ECB)
+
+def despad_ptext(text):
+    n = len(text) % 8
+    if n != 0:
+        return text + (' ' * (8 - n))
+    else:
+        return text
+
+def des_en(ptext, key):
+    cipher = des_cipher(key)
+    ptext = despad_ptext(ptext).encode('utf-8')
+    return cipher.encrypt(ptext)
+
+def des_de(ctext, key):
+    cipher = des_cipher(key)
+    return cipher.decrypt(ctext).decode('utf-8').rstrip()
+
+def despad_key(key):
+    return key.ljust(8)[:8]
+
+def main():
+    print("Welcome to DES (Original)")
+    ptext = input("Enter plaintext: ")
+    despad_ptext(ptext)
+    key = input("Enter key: ")
+    key = despad_key(key)
+    ctext = des_en(ptext, key)
+    print("Your ciphertext: ", ctext)
+    print("Your decrypted plaintext: ", des_de(ctext, key))
+
+if __name__ == '__main__':
+    main()