Computer Science
Efficient Security Mechanisms for Routing
Protocols
Yih-Chun Hu, Adrian Perrig, David B. Johnson
Presented by Yuzheng Zhou for CSC774
Secure Routing mechanisms in MANET
• Most previous secure routing mechanisms use
standard digital signatures
– Public key cryptography is expensive, especially
for MANET.
• Symmetric cryptography much more efficient
– Link state routing
– Distance vector routing: SEAD works, but is still
vulnerable for several attacks
– This paper propose four mechanisms addressing
secure distance vector/ path vector routing.
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Roadmap
•
•
•
Distance vector routing and attacks
Previous work - SEAD
Four mechanisms based on symmetric cryptography
–
Securing distance vector protocols
• Hash tree chain
• Tree-authenticated one-way chains
• Skiplists
– Securing path vector protocols
• Cumulative authentication
•
Conclusion and future work
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Distance vector routing
• Finds shortest paths between nodes in the
network
• Each router maintains a routing table list for all
possible destinations
address / distance (metric) / first hop
• Periodically transmits a routing update to each
of its neighbor routers
sequence / distance (metric)
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Attacks to Distance Vector Routing
•
•
•
•
Advertising short distances (blackhole)
Claim longer distances
Injecting routing loops
Inject a large number of route updates
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Previous work: SEAD
• SEAD (k=5, n=3)
• Attacks
– Same distance fraud
– Hash chain verification as long as O(ks)
– DoS attack for the nodes missing several routing updates
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Review: Merkle hash tree
•
To verify v2, need v3’, m01, m47, and verify
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Mechanism I: Hash Tree Chains
• Prevent same-distance fraud
• A hybrid between a hash tree and a one-way chain
– One-way chain property enforce that nodes cannot decrease the
distance metric (as in SEAD)
– Hash tree property is used to authenticate the node id.
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Hash Tree Chains (cont..)
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Mechanism II: Tree-authenticated one-way chains
• Speed up authentication of revived routing update
– O(ks)  O (k +log(s))
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Tree-authenticated one-way chains (cont..)
• Tree-authenticated one-way chains
– Use a new hash chain for each sequence
number
– All the hash chains are organized as a
merkle hash tree
– To authenticate anchor, following the path to
the root of the hash tree
– To authenticate update, using the anchor
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MW-chains (prepare for skiplists)
• Provides instant authentication and low storage
overhead for signatures
– This one-way chain contains a list of values-heads
– Between any two heads are a set of signature branches and a
set of checksum branches
– Sender uses a checksum chain that moves in the opposite
direction of the signature chains, to prevent an attacker from
forging an earlier message
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MW-chains (cont..)
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Mechanism III: Skiplists
• Goal: Prevent DoS attacks, speed up hash
chain authentication
• Method:
– Skip many steps in a virtual hash chain
– Skipchains can be embedded inside skiplists
– Represented by a MW-chain capable of signing
enough bits to ensure security
• A new head is chosen by hashing the head of this step
• Anchor of this skipchain is computed
• Sign this new anchor
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Skipchains
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Path vector routing
• Each routing update includes a list of routers
on the route
• Choose a route with the shortest recorded route
• Authenticate each hop the routing update has
traversed as recorded in the path
• Assure no hops were removed from that
recorded path
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Path vector routing (cont..)
• Traditional way of authentication:
– Each node inserts an authenticator in the packet,
recipient individually verify each authenticator
– Network overhead of carrying a MAC for each
node in the path
• Cumulative authentication
– A single MAC together with an ordered list of
nodes traversed by the packet
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Mechanism IV: Cumulative Authentication
• Each packet maintains a path authenticator
and an address list
• When packet traverses a node, the node append
its address to the address list
• Authenticate its position by replacing the path
authenticator with a MAC computed over the
received path authenticator and the packet’s
immutable fields
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Cumulative Authentication (cont..)
Example: to authenticate packet p, each node authenticate
using a MAC shared with target T
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Conclusions and future work
• Summary
– Presented four new mechanisms for secure
distance vector and path vector routing protocols
– Based on symmetric cryptography
– Use Merkle hash tree and M-W chain
• Future Work
– Decrease the overhead
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Computer Science
Thank you!
Q&A