Steven M. Bellovin

Learn More
Classical cryptographic protocols based on user chosen keys allow an attacker to mount password guessing attacks We introduce a novel combination of asymmetric public key and symmetric secret key cryptography that allow two parties sharing a common password to exchange con dential and authenticated information over an insecure network These proto cols are(More)
The current Internet infrastructure has very few built-in protection mechanisms, and is therefore vulnerable to attacks and failures. In particular, recent events have illustrated the Internet's vulnerability to both denial of service (DoS) attacks and flash crowds in which one or more links in the network (or servers at the edge of the network) become(More)
Pushback is a mechanism for defending against distributed denial-of-service (DDoS) attacks. DDoS attacks are treated as a congestion-control problem, but because most such congestion is caused by malicious hosts not obeying traditional end-to-end congestion control, the problem must be handled by the routers. Functionality is added to each router to detect(More)
The TCP/IP protocol suite, which is very widely used today, was developed under the sponsorship of the Department of Defense. Despite that, there are a number of serious security flaws inherent in the protocols, regardless of the correctness of any implementations. We describe a variety of attacks based on these flaws, including sequence number spoofing,(More)
We describe Just Fast Keying (JFK), a new key-exchange protocol, primarily designed for use in the IP security architecture. It is simple, efficient, and secure; we sketch a proof of the latter property. JFK also has a number of novel engineering parameters that permit a variety of tradeoffs, most notably the ability to balance the need for perfect forward(More)
There have been many attempts to measure how many hosts are on the Internet. Many of those end-points, however, are NAT boxes (Network Address Translators), and actually represent several different computers. We describe a technique for detecting NATs and counting the number of active hosts behind them. The technique is based on the observation that on many(More)
The encrypted key exchange (EKE) protocol is augmented so that hosts do not store cleartext passwords. Consequently, adversaries who obtain the one-way encrypted password file may (i) successfully mimic (spoof) the host to the user, and (ii) mount dictionary attacks against the encrypted passwords, but cannot mimic the user to the host. Moreover, the(More)
We describe JFK, a new key exchange protocol, primarily designed for use in the IP Security Architecture. It is simple, efficient, and secure; we sketch a proof of the latter property. JFK also has a number of novel engineering parameters that permit a variety of trade-offs, most notably the ability to balance the need for perfect forward secrecy against(More)
The Kerberos authentication system, a part of MIT's Project Athena, has been adopted by other organizations. Despite Kerberos's many strengths, it has a number of limitations and some weaknesses. Some are due to specifics of the MIT environment; others represent deficiencies in the protocol design. We discuss a number of such problems, and present solutions(More)
Conventional rewalls rely on topology restri tions and ontrolled network entry points to enfor e traÆ ltering. Furthermore, a rewall annot lter traÆ it does not see, so, e e tively, everyone on the prote ted side is trusted. While this model has worked well for small to medium size networks, networking trends su h as in reased onne tivity, higher line(More)