From 7dbeaff2fd3d71691752770070b1aae5ac3f80e9 Mon Sep 17 00:00:00 2001
From: Bill Buchanan <w.buchanan@napier.ac.uk>
Date: Tue, 9 Feb 2021 07:35:07 +0000
Subject: [PATCH] Update possible_ans.md

---
 unit02_symmetric/lab/possible_ans.md | 33 ++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/unit02_symmetric/lab/possible_ans.md b/unit02_symmetric/lab/possible_ans.md
index 433ab8c..4bb6f29 100644
--- a/unit02_symmetric/lab/possible_ans.md
+++ b/unit02_symmetric/lab/possible_ans.md
@@ -538,6 +538,39 @@ print ("  decrypt: "+plaintext)
 
 A sample is [here](https://repl.it/@billbuchanan/ch02ans07#main.py).
 
+## E.3
+In this case we will convert from Base-64 into a byte array and then try to decrypt:
+
+```python
+from Crypto.Cipher import AES
+import hashlib
+import sys
+import binascii
+import Padding
+import base64
+
+def decrypt(ciphertext,key, mode):
+	encobj = AES.new(key,mode)
+	return(encobj.decrypt(ciphertext))
+
+password = "hello"
+
+c='1jDmCTD1IfbXbyyHgAyrdg=='
+ciphertext = base64.b64decode(c)
+print ("Cipher (ECB): ",binascii.hexlify(ciphertext))
+
+
+key = hashlib.sha256(password.encode()).digest()
+
+plaintext = decrypt(ciphertext,key,AES.MODE_ECB)
+    
+plaintext = Padding.removePadding(plaintext.decode(),blocksize=Padding.AES_blocksize,mode='CMS')
+print ("  decrypt: ",plaintext)
+print ("  Key found: ",password)
+```
+
+A sample is [here](https://repl.it/@billbuchanan/ch02sample01#main.py).
+
 ## F.1
 Plaintext: norway