def decrypt_parameters_and_check_admin(input_string):
cipher = ctr_module(key, nonce)
plaintext = cipher.ctr(input_string)
if b";admin=true;" in plaintext:
return True
else:
return False
def encrypt_parameters(input_string):
# Quote out '=' and ';' from input string and convert to bytes
input_string = bytes(
input_string.replace(';', '%3B').replace('=', '%3D'), 'utf-8')
parameters_string = prefix + input_string + suffix
cipher = ctr_module(key, nonce)
ciphertext = cipher.ctr(parameters_string)
return ciphertext
def edit(ciphertext, offset, new_text):
key = b'YELLOW SUBMARINE'
nonce = struct.pack('Q', 0)
cipher = ctr_module(key, nonce) # Initialize cipher
# Because of the keystream nature of CTR we can encrypt a specific character at position 'offset' fairly easily
encrypted_new_text = cipher.ctr(bytes([0]) * offset + new_text)
# Then, slice the original ciphertext and inject the new text encrypted
prefix = ciphertext[:offset]
injection = encrypted_new_text[offset:]
suffix = ciphertext[offset + len(encrypted_new_text):]
chosen_ciphertext = prefix + injection + suffix
return chosen_ciphertext
def main():
# Set 01 - Challenge 07
target = base64.b64decode(open('set04challenge25.txt', 'r').read())
key = b'YELLOW SUBMARINE'
cipher = AES.new(key, AES.MODE_ECB)
plaintext = cipher.decrypt(target)
# Proceeding with current challenge
nonce = struct.pack('Q', 0)
cipher = ctr_module(b'YELLOW SUBMARINE', struct.pack('Q', 0))
ciphertext = cipher.ctr(plaintext)
recovered_plaintext = break_rw_ctr(ciphertext)
if recovered_plaintext != plaintext:
print("*** FAILED ***")
print("--- Success ---")
'''
import base64
import struct
from set03challenge18 import ctr_module
from os import urandom as get_random_bytes
from set01challenge02 import xor_strings
target = open('set03challenge19.txt', 'r').readlines()
target_list = [base64.b64decode(line) for line in target]
# Parameters
key = get_random_bytes(16)
nonce = struct.pack('Q', 0) # Expanded to 64bit little endian
cipher = ctr_module(key, nonce)
encrypted_target = [cipher.ctr(item) for item in target_list]
def single_character_decryption(encrypted_target, i):
# For each of the 256 possible guess-values:
for guess in range(256):
# Generate a list of all the 256 values of guess
# XOR'd against the value at index i of each ciphertext
decrypted = [
encrypted_item[i] ^ guess for encrypted_item in encrypted_target
]
# If all the XOR'd values are characters in the list provided,
# Then return the value of guess
if all([
chr(x)