Boston Key Party CTF 2014 Crypto 200

MITM II: Electric BoogalooCrypto : 200Chisa and Arisu are trying to tell each other two halves of a very important secret! They think they're safe, because they know how cryptography works---but can you learn their terrible, terrible secret? They're available as services at 54.186.6.201:12346 and 54.186.6.201:12345 respectively.http://bostonkeyparty.net/challenges/mitm2-632e4ecc332baba0943a0c6471dec2c6.tar.bz2

没什么可讲的，纯实现题。。。

#!/usr/bin/python# -*- coding: utf-8 -*-import base64import sysimport SocketServerimport mitmlibimport socketclass Person(object):def __init__(self, ip, port):self.s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)self.s.connect((ip, port))print "connected to %s" % ipdef gen_share(self):self.secretshare, self.publicshare = mitmlib.mkshare()def send_share(self):self.s.sendall(str(self.publicshare[0]) + "," + str(self.publicshare[1]))def recv_share(self):got = self.s.recv(2048).split(',')self.partpubshare = tuple([int(got[0]), int(got[1])])self.aeskey = mitmlib.mksecret(self.secretshare, self.partpubshare)def recv_check(self):msg = self.s.recv(400)#print msgcheck = mitmlib.decrypt(self.aeskey, msg)#print checkreturn checkdef send_enc(self, msg):self.s.send(mitmlib.encrypt(self.aeskey, msg))def recv_secret(self):return mitmlib.decrypt(self.aeskey, self.s.recv(400))def send_magic(self, magic):self.s.send(magic)def recv_magic(self):magic = self.s.recv(50)print magicif __name__ == '__main__':arisu = Person('54.186.6.201', 12345)chisa = Person('54.186.6.201', 12346)chisa.send_magic("アリスです")chisa.recv_magic()arisu.recv_magic()arisu.send_magic("千佐だよ")arisu.gen_share()chisa.gen_share()arisu.recv_share()arisu.send_share()chisa.send_share()chisa.recv_share()cnt = 0while cnt < 19:cnt += 1print cntcheck_a = arisu.recv_check()chisa.send_enc(check_a)check_b = chisa.recv_check()arisu.send_enc(check_b)secret = arisu.recv_secret()print secretchisa.send_enc(secret)print chisa.recv_secret()