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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.
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
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)
Attacks to Distance Vector Routing • Advertising short distances (blackhole) • Claim longer distances • Injecting routing loops • Inject a large number of route updates
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
Review: Merkle hash tree • To verify v2, need v3’, m01, m47, and verify
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.
Mechanism II: Tree-authenticated one-way chains • Speed up authentication of revived routing update • O(ks) O (k +log(s))
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
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
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
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
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
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
Cumulative Authentication (cont..) Example: to authenticate packet p, each node authenticate using a MAC shared with target T
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