cryptopals

commit 814fdcda46c0c9f20c1da3a6951b1e4a9794fba9
parent aa547d9e5852613ca58577c698e8e8d964ba17ed
Author: mpizzzle <michael.770211@gmail.com>
Date:   Sat, 16 Feb 2019 23:03:05 +0000

challenge 26 complete

Diffstat:
A
set4/ctr_bitflipping_attacks.py
 | 
23
+++++++++++++++++++++++

1 file changed, 23 insertions(+), 0 deletions(-)
diff --git a/set4/ctr_bitflipping_attacks.py b/set4/ctr_bitflipping_attacks.py
@@ -0,0 +1,23 @@
+import re
+from Crypto.Cipher import AES
+from Crypto import Random
+from Crypto.Util import Counter
+
+key = Random.new().read(AES.block_size)
+
+def encrypt(plaintext):
+    return AES.new(key, AES.MODE_CTR, counter=Counter.new(128)).encrypt(plaintext)
+
+def decrypt_and_parse(cipher):
+    return ";admin=true;" in encrypt(cipher)
+
+def encryption_oracle(m):
+    return encrypt("comment1=cooking%20MCs;userdata=" + re.sub("[;|=]", '', m) + ";comment2=%20like%20a%20pound%20of%20bacon")
+
+plaintext = "hello-admin-true"
+ciphertext = list(encryption_oracle(plaintext))
+
+ciphertext[(2 * AES.block_size) + 5] = chr(ord('-') ^ ord(';') ^ ord(ciphertext[(2 * AES.block_size) + 5]))
+ciphertext[(2 * AES.block_size) + 11] = chr(ord('-') ^ ord('=') ^ ord(ciphertext[(2 * AES.block_size) + 11]))
+
+print decrypt_and_parse(''.join(ciphertext))