cryptopals

commit a860e4e4bdbfb3542f23bfb91aaf23fa8dea5e8d
parent c2b2be0007dea5f4d526f313fcfd0934c9fd5b2b
Author: mpizzzle <michael.770211@gmail.com>
Date:   Sun,  8 Oct 2017 18:25:51 +0100

set 2 challenge 12 complete, a few steps missing though

Diffstat:
A
set2/byte_at_a_time_ecb_decryption.py
 | 
31
+++++++++++++++++++++++++++++++

1 file changed, 31 insertions(+), 0 deletions(-)
diff --git a/set2/byte_at_a_time_ecb_decryption.py b/set2/byte_at_a_time_ecb_decryption.py
@@ -0,0 +1,31 @@
+import sys
+from Crypto.Cipher import AES
+from Crypto import Random
+from Crypto.Random import random
+
+def random_key():
+    return Random.new().read(AES.block_size)
+
+def encryption_oracle(key, msg):
+    plaintext = msg
+
+    if len(msg) % 16 != 0:
+        for i in range(16 - (len(msg) % 16)):
+            msg += '\x04'
+
+    return AES.new(key, AES.MODE_ECB).encrypt(msg)
+
+pt1 = "Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkg\n"
+pt2 = "aGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBq\n"
+pt3 = "dXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUg\n"
+pt4 = "YnkK"
+aaa = "AAAAAAAAAAAAAAA"
+
+plaintext = aaa + str(pt1 + pt2 + pt3 + pt4).decode("base64") # no peeking!
+key = random_key()
+
+for i in range(len(plaintext)):
+    dict = {encryption_oracle(key, aaa + chr(j)) : chr(j) for j in range(0xff)}
+    cipher = encryption_oracle(key, plaintext[i:])
+    sys.stdout.write(dict[cipher[:AES.block_size]])
+    aaa = aaa[1:]  + dict[cipher[:AES.block_size]]