VIII Кубок CTF России | Канал
Channel
949
subscribers
Восьмой эпизод самого легендарного российского CTF-соревнования
Связь: @deviantwish
Telegram Center
Channel
Проспект Мира 119, стр. 461)import sage.all
from sage.modules.free_module_integer import IntegerLattice
import os
import sys
Q = 31337
P = 2**64
W = 31337
MIDDLE_LETTER = ord("n")
def poly_hash(a):
if type(a) == str:
a = a.encode()
h = 0
for el in a:
h = (h * Q + el) % P
return h
def string_for_target_hash(target: int, string_len: int = 200) -> bytes:
known = [MIDDLE_LETTER] * string_len
known_hash = poly_hash(known)
L = IntegerLattice(
[
[W * Q ** (len(known) - i - 1)]
+ [1 if j == i else 0 for j in range(len(known))]
for i in range(len(known))
]
+ [[W * P] + [0] * len(known)]
)
vector = L.approximate_closest_vector(
[W * (target - known_hash)] + [0] * len(known)
)
print(vector)
return bytes(k + v for k, v in zip(known, vector[1:]))