Matthias Horst Martin Grothe Tibor Jager Jörg Schwenk Breaking PPTP VPNs via RADIUS Encryption. 159-175 2016 CANS https://doi.org/10.1007/978-3-319-48965-0_10 conf/cans/2016 db/conf/cans/cans2016.html#HorstGJS16