InterKosenCTF - pascal homomorphicity

pascal_homomorphicity.py

from pwn import *

s = remote('crypto.kosenctf.com', 8002)
s.recvline()

encrypted = int(s.recvline())
s.recvline()

table = ''.join(sorted('{}abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789_- !?#'))

l = 48
known = 'KosenCTF{'
for _ in range(len(known), l):
  p = ''

  for c in table:
    temp = int((known + c).ljust(l, '\0').encode('hex'), 16)

    s.recvuntil('> ')
    s.sendline(str(temp))
    s.recvline()
    res = int(s.recvline())

    if res > encrypted:
      known += p
      break
    p = c

  print known