[XNUCA2018]Warmup
题目
Buggy_Server.py
from Crypto.Util.number import bytes_to_long, getPrime
from random import randint
from gmpy2 import powmod
import sys
p = getPrime(1024)
q = getPrime(1024)
N = p*q
Phi = (p-1)*(q-1)
with open("flag", 'r') as fr:
flag = bytes_to_long(fr.read().strip())
def get_enc_key(BitLen, Phi):
e = getPrime(BitLen)
if Phi % e == 0:
return get_enc_key(BitLen, Phi)
else:
return e
def sprint(message):
print(message)
sys.stdout.flush()
def communicate():
sprint("This is a message distribute system. Please tell me your name: ")
user = raw_input()
bakcdoor(user)
e = get_enc_key(randint(13, 13 + (len(user) % 4)), Phi)
ct = powmod(flag, e, N)
sprint("Hi %s, your N is: %d\nAnd your exponent is: %d\nLast but not least, your secret is: %d" % (user, N, e, ct))
sprint("You will know the secret after I give you P,Q.\nSee you next time!")
if __name__ == "__main__":
communicate()
sniffed.pcapng
解题