Transcript Slides

SPINS: Security Protocols for
Sensor Networks
Adrian Perrig et al.
University of California, Berkeley
Mobicom 2001
Presenter: Ryan Babbitt
Outline
 Background
 Protocols
 SNEP
 μTESLA
 Example applications
 Authenticated Routing
 Node-to-node key agreement
 Conclusions
Background
 Sensor networks
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Nodes
Base stations
Communication channel
Communication patterns
Trust framework
Resource restrictions
Security Goals for Sensor Networks
 Data Confidentiality
 Semantic security
 Data Authentication
 Point-to-point
 Broadcast
 Data Integrity
 Data Freshness
 Weak
 Strong
Notation
Secure Network Encryption Protocol
(SNEP)
 Purpose: secure two-party communication
 Elements
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Symmetric key
Message Authentication Code
Block cipher in counter mode
 Shared counter
SNEP Communication
 Weak Version
 Strong Version
SNEP Implementation
 Key Setup
 Bootstrap secret master key
 Key generation
 Encryption
 RC5
 Message Authentication Code
 CBC-MAC (one per packet)
 {M}KE, MAC(KMAC, {M}KE)
SNEP Questions
 What if counters lose
synchronization?
 What if packets are lost (MAC)?
μTESLA
 Purpose: authenticated broadcast
 Phases
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Sender setup
Broadcasting
Bootstrapping receivers
Receiving broadcast packets
μTESLA – Sender Side
 Key chain generation
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Randomly pick last key Kn
Repeatedly apply one-way function F
Fn(Kn) <- ... <- F(F(F(Kn)) <- F(F(Kn) <- F(Kn) <- Kn
K0 = F(K1) = F(F(K2) = …
 Broadcast
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Key disclosure schedule
 Time intervals
 Current key
 Interval offset
μTESLA – Receiver Side
 Bootstrapping new receivers
 Key commitment
 Loose time synchronization
 Key disclosure schedule
 Authenticating packets
 Check “security condition”
Applications
 Authenticated routing
 Build routing tree based on authenticated
packets received
 Pair-wise key agreement
Questions
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What
What
What
What
about broadcast confidentiality?
if too many keys are lost?
if a node wants to broadcast?
about group communication?
Conclusions
 SNEP
 Basic node-to-base station security
 Susceptible to synchronization loss?
 Susceptible to packet loss?
 μTESLA
 Authenticated broadcast
 No confidentiality
 Scalability problems
 Node broadcast
 Pairwise/group communication
Performance