Update possible_ans.md

unit02_symmetric/lab/possible_ans.md

@@ -1,11 +1,71 @@
 ## A.1 
 openssl list-cipher-commands
+
 openssl version
+
 openssl prime –hex 1111
+
 openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin
+
 openssl enc -aes-256-cbc -in myfile.txt -out encrypted.bin –base64
+
 openssl enc -d -aes-256-cbc -in encrypted.bin -pass pass:napier -base64
 
+## D1
+```python
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes 
+from cryptography.hazmat.primitives import padding
+
+import hashlib
+import sys
+import binascii
+
+val='hello'
+password='hello'
+
+plaintext=val
+
+def encrypt(plaintext,key, mode):
+    method=algorithms.AES(key)
+    cipher = Cipher(method, mode)
+    encryptor = cipher.encryptor()
+    ct = encryptor.update(plaintext) + encryptor.finalize()
+    return(ct)
+
+def decrypt(ciphertext,key, mode):
+    method=algorithms.AES(key)
+    cipher = Cipher(method, mode)
+    decryptor = cipher.decryptor()
+    pl = decryptor.update(ciphertext) + decryptor.finalize()
+    return(pl)
+
+def pad(data,size=128):
+    padder = padding.PKCS7(size).padder()
+    padded_data = padder.update(data)
+    padded_data += padder.finalize()
+    return(padded_data)
+
+def unpad(data,size=128):
+    padder = padding.PKCS7(size).unpadder()
+    unpadded_data = padder.update(data)
+    unpadded_data += padder.finalize()
+    return(unpadded_data)
+
+key = hashlib.sha256(password.encode()).digest()
+
+plaintext=pad(plaintext.encode())
+
+print("After padding (CMS): ",binascii.hexlify(bytearray(plaintext)))
+
+ciphertext = encrypt(plaintext,key,modes.ECB())
+print("Cipher (ECB): ",binascii.hexlify(bytearray(ciphertext)))
+
+plaintext = decrypt(ciphertext,key,modes.ECB())
+
+plaintext = unpad(plaintext)
+print("  decrypt: ",plaintext.decode())
+
+```
 
 
 ## D2
@@ -97,61 +157,7 @@ Cipher (ECB):  b'b2a350deec0b0718'
 
 
 
-## D.3
-Answer:
-* /vA6BD+ZXu8j6KrTHi1Y+w== - italy
 
-```python
-from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes 
-from cryptography.hazmat.primitives import padding
-from cryptography.hazmat.backends import default_backend
-
-import hashlib
-import binascii
-import base64
-
-password='hello'
-
-
-def encrypt(plaintext,key, mode):
-    method=algorithms.AES(key)
-    cipher = Cipher(method,mode, default_backend())
-    encryptor = cipher.encryptor()
-    ct = encryptor.update(plaintext) + encryptor.finalize()
-    return(ct)
-
-def decrypt(ciphertext,key, mode):
-    method=algorithms.AES(key)
-    cipher = Cipher(method, mode, default_backend())
-    decryptor = cipher.decryptor()
-    pl = decryptor.update(ciphertext) + decryptor.finalize()
-    return(pl)
-
-def pad(data,size=128):
-    padder = padding.PKCS7(size).padder()
-    padded_data = padder.update(data)
-    padded_data += padder.finalize()
-    return(padded_data)
-
-def unpad(data,size=128):
-    padder = padding.PKCS7(size).unpadder()
-    unpadded_data = padder.update(data)
-    unpadded_data += padder.finalize()
-    return(unpadded_data)
-
-key = hashlib.sha256(password.encode()).digest()
-
-
-cipher='/vA6BD+ZXu8j6KrTHi1Y+w=='
-ciphertext = base64.b64decode(cipher)
-print("Cipher (ECB): ",binascii.hexlify(bytearray(ciphertext)))
-
-plaintext = decrypt(ciphertext,key,modes.ECB())
-
-plaintext = unpad(plaintext)
-print("  decrypt: ",plaintext.decode())
-```
-A sample is [here](https://repl.it/@billbuchanan/ch02ans05#main.py).
 
 ## E.1
 Answers:
@@ -268,35 +274,60 @@ 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:
 
+Answer:
+* /vA6BD+ZXu8j6KrTHi1Y+w== - italy
+
 ```python
-from Crypto.Cipher import AES
+from cryptography.hazmat.primitives.ciphers import Cipher, algorithms, modes 
+from cryptography.hazmat.primitives import padding
+from cryptography.hazmat.backends import default_backend
+
 import hashlib
-import sys
 import binascii
-import Padding
 import base64
 
+password='hello'
+
+
+def encrypt(plaintext,key, mode):
+    method=algorithms.AES(key)
+    cipher = Cipher(method,mode, default_backend())
+    encryptor = cipher.encryptor()
+    ct = encryptor.update(plaintext) + encryptor.finalize()
+    return(ct)
+
 def decrypt(ciphertext,key, mode):
-	encobj = AES.new(key,mode)
-	return(encobj.decrypt(ciphertext))
+    method=algorithms.AES(key)
+    cipher = Cipher(method, mode, default_backend())
+    decryptor = cipher.decryptor()
+    pl = decryptor.update(ciphertext) + decryptor.finalize()
+    return(pl)
 
-password = "hello"
-
-c='1jDmCTD1IfbXbyyHgAyrdg=='
-ciphertext = base64.b64decode(c)
-print ("Cipher (ECB): ",binascii.hexlify(ciphertext))
+def pad(data,size=128):
+    padder = padding.PKCS7(size).padder()
+    padded_data = padder.update(data)
+    padded_data += padder.finalize()
+    return(padded_data)
 
+def unpad(data,size=128):
+    padder = padding.PKCS7(size).unpadder()
+    unpadded_data = padder.update(data)
+    unpadded_data += padder.finalize()
+    return(unpadded_data)
 
 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).
+cipher='/vA6BD+ZXu8j6KrTHi1Y+w=='
+ciphertext = base64.b64decode(cipher)
+print("Cipher (ECB): ",binascii.hexlify(bytearray(ciphertext)))
+
+plaintext = decrypt(ciphertext,key,modes.ECB())
+
+plaintext = unpad(plaintext)
+print("  decrypt: ",plaintext.decode())
+```
+A sample is [here](https://repl.it/@billbuchanan/ch02ans05#main.py).
 
 ## F.1
 Plaintext: norway