Cryptanalysis of Microsoft's point-to-point tunneling protocol (PPTP)
Bruce Schneier, Mudge · 1998
The Point-t&Point Meting Protocol (PPTP) is used to secure PPP connection over TCP/R ~. h this paper we ansdyze Microsoft's Windows NT impl~ mentation of PPTP.We show how to break both the chWenge/r=ponse authentication protocol (Microsoft C~P)and the RC4 encryption protocol (MPPE), as weU x how to attack the control channel in Microsoft's implementation.Th=e attacks do not nec-tiy break PPTP, but ody Microsoft's implementation of the pr~ tocol.-, ..,. . .!