CLASS 7 Sybil, Sybil, Sybil, Sybil, Sybil Secure Networks and Distributed Systems cis.ksu

1. CLASS 7Sybil, Sybil, Sybil, Sybil, SybilSecure Networks and Distributed Systemshttp://www.cis.ksu.edu/~eyv/CIS890_F10/

2. Administrative notes If you have not yet done so, sign up for paper presentations If you have not yet done so, submit project proposals I will return proposals with comments on Monday (a week from today) Revisions are due a week from that Monday. Revised proposals are a �contract� that you will do the project you proposed

3. How is Sybil possible? What do we know about a computer On the Internet On the local WAN On the local LAN What do we know about people on the Internet? �On the Internet, no one can tell if you�re a dog� Corollary: �On the Internet, no one can tell if a pack of wolves is a single dog�

4. How can we stop it? We can�t! Well, not in the general case� What about application-specific? Trusted authorities Reputation systems (NO!) Physically unclonable functions, or physical one-way functions (device fingerprinting) CAPTCHAs/CPU puzzles (see: https://www.dtc.umn.edu/weis2004/clayton.pdf) Social networks

5. SybilLimit: A Near-Optimal Social Network Defense against Sybil Attacks Haifeng Yu, Phillip B. Gibbons, Michael Kaminsky, and Feng Xiao

6. A quick review of O-notation o(f(n)) Exists g(n): f(n) = g(n)*e for all e O(f(n)) Exists: g(n): f(n) = k*g(n) for some k T(f(n)) Exist g(n): k*g(n) = f(n) = k�*g(n) for some k, k� O Exists: g(n): k*g(n) = f(n) for some k

7. A quick network primer Random graph (e.g. Erd�s�R�nyi) Has some nice provable properties Scale-free network Power law distribution of connections: hubs Small-world network Hubs + short paths Mixing �time�