Skip to content

Instantly share code, notes, and snippets.

Created July 16, 2022 17:20
  • Star 0 You must be signed in to star a gist
  • Fork 0 You must be signed in to fork a gist
Star You must be signed in to star a gist
What would you like to do?
#!/usr/bin/env python3
from Crypto.Util.number import *
import sys
from flag import flag
def diff(a, b):
assert a.bit_length() == b.bit_length()
w, l = 0, a.bit_length()
for _ in range(l):
if bin(a)[2:][_] != bin(b)[2:][_]: w += 1
return w
def die(*args):
def pr(*args):
s = " ".join(map(str, args))
sys.stdout.write(s + "\n")
def sc():
return sys.stdin.readline().strip()
def main():
border = "|"
pr(border, "Hello guys! This is a challenge on fault attack for signatures, our ", border)
pr(border, "storage can apply at most `l' bit flip-flop on signature modulus, so", border)
pr(border, "try to locate the critical bits, we'll changed them to forge a sign!", border)
nbit = 512
p, q = [getPrime(nbit) for _ in '__']
n, e = p * q, 65537
B, l = [int(b) for b in bin(n)[2:]], 2
MSG = "4lL crypt0sy5t3ms suck5 fr0m faul7 atTaCk5 :P"
m = bytes_to_long(MSG.encode('utf-8'))
while True:
pr("| Options: \n|\t[A]pply fault \n|\t[G]et the parameters \n|\t[V]erify the signature \n|\t[Q]uit")
ans = sc().lower()
if ans == 'a':
_B = B
pr(border, f"please send at most {l}-tuple array from indices of bits of modulus, like: 14, 313")
ar = sc()
ar = [int(_) for _ in ar.split(',')]
if len(ar) <= l:
for i in range(len(ar)): _B[ar[i]] = (_B[ar[i]] + 1) % 2
N = int(''.join([str(b) for b in _B]), 2)
else: raise Exception('Invalid length!')
except: pr(border, "Something went wrong!!")
elif ans == 'g':
pr(border, f'e = {e}')
pr(border, f'n = {n}')
elif ans == "v":
pr(border, "please send signature to verify: ")
_flag, signature = False, sc()
signature = int(signature)
if pow(signature, e, N) == m: _flag = True
else: pr(border, "Your signature is not valid!!")
pr(border, "Something went wrong!!")
if _flag: die(border, "Congrats! your got the flag: " + flag)
elif ans == 'q': die("Quitting ...")
else: die("Bye bye ...")
if __name__ == "__main__": main()
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment