diff --git a/index.py b/index.py
index 57a7253..3586689 100644
--- a/index.py
+++ b/index.py
@@ -7,6 +7,11 @@ def caesar(ptextletter, keyletter):
     return chr((ptextNum + keyletterNum) % 26 + ord('A'))
 
 
+def caesar_reverse(ptextletter, keyletter):
+    ptextNum = ord(ptextletter) - ord('A')
+    keyletterNum = ord(keyletter) - ord('A')
+    return chr((ptextNum - keyletterNum) % 26 + ord('A'))
+
 def encryption(plaintext, key):
     ciphertext = ''
     for i in range(len(plaintext)):
@@ -15,21 +20,24 @@ def encryption(plaintext, key):
 
 
 def decryption(ciphertext, key):
-    return ciphertext
+    plaintext = ''
+    for i in range(len(ciphertext)):
+        plaintext += caesar_reverse(ciphertext[i], key[i % len(key)])
+    return plaintext
 
 
 def main():
     # parse command line argument
     parser = argparse.ArgumentParser()
-    parser.add_argument('--ptext', type=str)
+    parser.add_argument('--text', type=str)
     parser.add_argument('--key', type=str)
     args = parser.parse_args()
 
     key = args.key
-    ciphertext = encryption(args.ptext, key)
+    user_text = args.text
 
-    print("Ciphertext: " + ciphertext)
-    print("Decrypted plaintext: " + decryption(ciphertext, key))
+    print("Ciphertext: " + encryption(user_text, key))
+    print("Decrypted plaintext: " + decryption(user_text, key))
 
 
 if __name__ == '__main__':