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from pwn import *
import random
import subprocess
import sys
import time
# MT19937 constants
W, N, M, R = 32, 624, 397, 31
A = 0x9908B0DF
w_upper = (1 << W) - (1 << R)
w_lower = (1 << R) - (1 << 0)
w_full = (1 << W) - (1 << 0)
def _mask_lower(n):
return (1 << n) - (1 << 0)
def mask_lower(bits, n, shl):
mask = _mask_lower(n)
return (bits & mask) << shl
def _mask_upper(n):
return (1 << W) - (1 << (W - n))
def mask_upper(bits, n, shr):
mask = _mask_upper(n)
return (bits & mask) >> shr
def undo_selfxor(bits, mask, shr, shl):
dirty = (mask << shl) >> shr
clean = w_full ^ dirty
assert(dirty == (dirty & w_full))
rec = bits & clean
while dirty != 0:
pre = clean & ((dirty << shr) >> shl)
post = ((pre << shl) >> shr) & w_full
assert(pre != 0) # we can recover new bits
rec |= (((rec & pre) << shl) >> shr) ^ (bits & post)
clean |= post
dirty &= w_full ^ clean
return rec
def harden(bits):
bits ^= mask_upper(bits, W - 11, 11)
bits ^= mask_lower(bits, W - 7, 7) & 0x9d2c5680
bits ^= mask_lower(bits, W - 15, 15) & 0xefc60000
bits ^= mask_upper(bits, W - 18, 18)
return bits
def unharden(bits):
bits = undo_selfxor(bits, _mask_upper(W - 18), 18, 0)
bits = undo_selfxor(bits, _mask_lower(W - 15) & (0xefc60000 >> 15), 0, 15)
bits = undo_selfxor(bits, _mask_lower(W - 7) & (0x9d2c5680 >> 7), 0, 7)
bits = undo_selfxor(bits, _mask_upper(W - 11), 11, 0)
return bits
val = random.getrandbits(32)
assert(unharden(harden(val)) == val)
# for initial state population from seed
def mul_a(x):
return (x >> 1) ^ (A * (x & 1))
def gen_next(states):
si = len(states)
x = (states[si - N] & w_upper) | (states[si - N + 1] & w_lower)
return states[si - N + M] ^ mul_a(x)
def main(host="localhost", port="9051"):
io = remote(host, int(port))
retries = 100
good = 9
values = []
for n in range(retries):
assert(io.readline() == b"Hints:\n")
for i in range(good):
values.append(unharden(int(io.readline())))
assert(io.readline() == b"Guess:\n")
if n == retries - 1:
break
values.append(None)
io.sendline(b"0")
predict = gen_next(values)
io.sendline(str(harden(int(predict))).encode())
print(io.readline().decode())
if __name__ == "__main__":
main(*sys.argv[1:])
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