MS-CHAPv2 is an authentication and key negotiation protocol that, while old and battered, is still unfortunately deployed quite widely. It underpins almost all PPTP VPN services, and is relied upon by many WPA2 Enterprise wireless deployments. We will release tools that definitively break the protocol, allowing anyone to affordably decrypt any PPTP VPN traffic or CHAPv2-based WPA2 handshake with a 100% success rate.