import collections
import random
import string
import unittest
from Crypto.Cipher import AES
from Crypto.Util import py3compat
import padlib, stringlib
KEY = 'x]ln6jSC=Fk&b43Q'
BLOCKSIZE = 16
BASE64_SUFFIX = "Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkgaGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBqdXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUgYnkK"
SUFFIX = stringlib.decode_base64(BASE64_SUFFIX).decode("ascii")
def encryption_oracle(plaintext, suffix=SUFFIX, key=KEY):
cipher = AES.new(key, AES.MODE_ECB)
plaintext = padlib.pad_pkcs7(plaintext + suffix, BLOCKSIZE)
return cipher.encrypt(plaintext)
def solve(msg_len, bs):
dec_msg = []
test_7block = "a" * (bs - 1)
for block_idx in range((msg_len + bs - 1) // bs):
for byte_offset in range(bs):
if block_idx * bs + byte_offset >= msg_len:
return ''.join(dec_msg)
shift_pad = (bs - byte_offset - 1) * "a"
ciphertext = encryption_oracle(shift_pad)
target_block = ciphertext[bs * block_idx: bs * (block_idx + 1)]
import collections
import random
import string
import unittest
from Crypto.Cipher import AES
from Crypto.Util import py3compat
import padlib, stringlib
KEY = 'x]ln6jSC=Fk&b43Q'
BLOCKSIZE = 16
BASE64_SUFFIX = "Um9sbGluJyBpbiBteSA1LjAKV2l0aCBteSByYWctdG9wIGRvd24gc28gbXkgaGFpciBjYW4gYmxvdwpUaGUgZ2lybGllcyBvbiBzdGFuZGJ5IHdhdmluZyBqdXN0IHRvIHNheSBoaQpEaWQgeW91IHN0b3A/IE5vLCBJIGp1c3QgZHJvdmUgYnkK"
SUFFIX = stringlib.decode_base64(BASE64_SUFFIX).decode("ascii")
def encryption_oracle(plaintext, suffix=SUFFIX, key=KEY):
cipher = AES.new(key, AES.MODE_ECB)
plaintext = padlib.pad_pkcs7(plaintext + suffix, BLOCKSIZE)
return cipher.encrypt(plaintext)
def solve(msg_len, bs):
dec_msg = []
test_7block = "a" * (bs - 1)
for block_idx in range((msg_len + bs - 1) // bs):
for byte_offset in range(bs):
if block_idx * bs + byte_offset >= msg_len:
return ''.join(dec_msg)
shift_pad = (bs - byte_offset - 1) * "a"
ciphertext = encryption_oracle(shift_pad)
def solve(base64_ciphertext, key, nonce):
prefix = struct.pack('<Q', nonce)
ctr = Counter.new(64, prefix=prefix, initial_value=0, little_endian=True)
cipher = AES.new(key, AES.MODE_CTR, counter=ctr)
ciphertext = stringlib.decode_base64(base64_ciphertext)
return cipher.decrypt(ciphertext)
def solve(key, filename):
cipher = AES.new(key, AES.MODE_ECB)
with open(filename, "r") as f:
ciphertext = ''.join(line.rstrip() for line in f.readlines())
unbase64 = stringlib.decode_base64(ciphertext)
return cipher.decrypt(unbase64)
