lecture17-ad-hoc-net-keyest

lecture17-ad-hoc-net-keyest - Lecture 17 Ad Hoc Network Key...

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3/19/09 1 1 Lecture 17 Ad Hoc Network Key Establishment Adrian Perrig 18-731: Network Security Spring 2009 2 Overview Administrative issues Miniproject 1 experiences Midterm graded, midterm grades available on blackboard soon Research project progress Changes to course based on midsemester feedback Final exam scheduling issues Upcoming lectures Ad hoc and sensor network security
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3/19/09 2 3 Ad Hoc Network Routing Each device acts as a router Routing protocol discovers paths through network Nodes have limited resources A B C 4 Safety-Critical Ad Hoc Network Applications Ad hoc networks provide connectivity in safety-critical environments Vehicular ad hoc networks (VANETs) Corporate ad hoc networks connecting mobile manufacturing devices Emergency response, disaster relief Devices protecting critical infrastructures Satellite networks in space Military applications
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3/19/09 3 5 Ad Hoc Networks Properties Mobile! Wireless communication Medium to high bandwidth High variability of connection No fixed infrastructure Participants from different administrative domains Medium to high computation, memory Usually human user with each device 6 Key Establishment Seen So Far SSL/TLS Assumption: browser can authenticate server’s certificate with its local CA root certificates Large-group key distribution Assumption: each client already has a secure connection to key distribution server Challenge in ad hoc networks: establish keys without any prior trust relationships
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3/19/09 4 7 Problem Definition Goals Secure, authenticated communication between devices that share no prior context Demonstrative identification : ensure to human user which other device they are communicating with No prior context? No CAs or other trusted authorities No PKI No shared secrets No shared communication history Problem reduces to key establishment Diffie & Hellman taught us how to share secrets… 8 Diffie-Hellman Key Agreement Public values: large prime p, generator g Alice has secret a, Bob has secret b A B: g a mod p B A: g b mod p Bob: (g a mod p) b mod p = g ab mod p Alice: (g b mod p) a mod p = g ab mod p Eve cannot compute g ab mod p Are we done?
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5 9 Problem: Man-in-the-middle Attack Mallory can impersonate Alice to Bob, and impersonate Bob to Alice! A M: g a mod p M A: g m mod p M B: g m mod p B M: g b mod p Bob: (g m mod p) b mod p = g bm mod p Alice: (g m mod p) a mod p = g am mod p 10 How Serious is MitM Attack? Wireless communication is invisible People can’t tell which devices are connected Neighbor can easily execute MitM attack If neighbor has a faster computer, it can easily respond faster than the legitimate devices Easy to perform with high success rate! Solutions?
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lecture17-ad-hoc-net-keyest - Lecture 17 Ad Hoc Network Key...

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