Cryptanalysis of Microsoft's Point-to-Point Tunneling Protocol
Li Jian · Jisuanji gongcheng · 2002
The point-to-point tunneling protocol (PPTP) is used to secure PPP connections over TCP/IP links. In this paper we analyze Microsoft's Windows NT implementation of PPTP. We show how to break both the challenge/response authentication protocol (Microsoft CHAP) and the RC4 encryption protocol (MPPE), as well as how to attack the control channel in Microsoft's implementation. These attacks needn't break PPTP, but only Microsoft's implementation of the protocol.