bcrypt.ctf/bcrypt/bcrypt.py
2025-06-21 17:42:00 +10:00

109 lines
2.7 KiB
Python

from math import gcd
from random import randint, randbytes
H = 18446744073709551614
K = 59275109328752
M = 2**64
def Rjb(j: int, b: int) -> int:
return b << j**2
def Rb(b: int) -> int:
Rb = 0
for j in range(8):
Rb ^= Rjb(j, b)
return Rb
'''
Returns a hashmap (python dictionary) of b -> R(b)
for all b such that: min < b < max
'''
def precompute_R(min: int,
max: int) -> dict[int, int]:
b = min
R_table = {}
while b <= max:
R_table[b] = Rb(b)
b += 1
return R_table
def hashfn(x: bytes, R_table: dict[int, int]) -> int:
h = -2
for i in range(len((x))):
b = x[i]
h = h**2 * (b+1) + ((K * (i+1)) ^ R_table[b])
h %= M
return h % M
def bcrypt(x: bytes) -> int:
h = 18446744073709551614
for (i, b) in enumerate(x):
h *= h * (b + 1)
k = 59275109328752 * (i + 1)
for j in range(8):
k ^= b << (j * j)
h += k
h %= (2 ** 64)
return h
def debug_hashes_eq(x: bytes, R_table: dict[int, int]) -> bool:
return hashfn(x, R_table) == bcrypt(x)
def debug_test_random_hashes(trials: int,
max_bytes: int = 16,
quiet: bool = False) -> bytes | None:
R_table = precompute_R(0, 255)
for i in range(trials):
# generate random bytes
num_bytes = randint(0, max_bytes)
x = randbytes(num_bytes)
# test the modified bcrypt with the original
hash_test = hashfn(x, R_table)
hash_bcrypt = bcrypt(x)
if hash_test != hash_bcrypt:
if not quiet:
print(f'Your hashfn sucks, big mistake bucko!! (iter: {i})')
print(hash_test)
print(hash_bcrypt)
print([str(b) for b in x])
return x
if not quiet:
print('Impeccable hashfn holy moly!!')
return None
def main() -> None:
print(f'gcd(H,K): {gcd(H,K)}')
print(f'gcd(H,M): {gcd(H,M)}')
print(f'gcd(K,M): {gcd(K,M)}')
if debug_test_random_hashes(10000) != None:
R_table = precompute_R(0, 255)
x = bytes(input('x: '), 'utf-8')
hash_test = hashfn(x, R_table)
hash_bcrypt = bcrypt(x)
print(f'hashfn: {hash_test}')
print(f'bcrypt: {hash_bcrypt}')
# a = bytes(input("A: "), 'utf-8')
# b = bytes(input("B: "), 'utf-8')
# if a != b and hashfn(a) == hashfn(b):
# print('*** YOU WIN ***')
# elif a == b:
# print('Idiot those are the same')
# else:
# print("Trivially false!")
if __name__ == '__main__':
try:
main()
except KeyboardInterrupt:
print('\n[!] Received SIGINT')
except EOFError:
print('\n[!] Reached EOF')