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Random Key-Assignment for Secure Wireless Sensor Networks
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Random Key-Assignment for Secure Wireless Sensor
NetworksRoberto Di Pietro, Luigi V. Mancini and
Alessandro Mei
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Limited memory Limited computational power Limited energy
Sensor nodes
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Secure microcontroller
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Passive attacks◦ Cipher text attacks
Active attacks◦ Take control of a sensor node
Unfriendly environment Nodes only trust themselves
Threat Model
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Secure pairwise communication Memory efficient Energy efficient Tolerate the collusion of a set of corrupted
sensors
Goals
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Have one master key◦ Can’t tolerate nodes being taken over
Each node stores a seperate key for every other node◦ Requires too much space◦ Expensive to add more nodes later
Tradeoff◦ Use less memory, but have only a probabilistic
tolerance to nodes being taken over
Naïve solutions
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One way hash function Symmetric encryption Keyed hashed function Pseudo-random number generator
Requirements
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A key deployment scheme A key discovery procedure A security adaptive channel establishment
procedure
The direct protocol
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Method used in A key-managementscheme for distributed sensor networks:
A pool of P random keys is generated Each sensors takes k random keys from the
pool
Key deployment
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Challenge is encrypted using each key and then broadcasted
Needs to perform k^2 decryptions on receiver side and k encryptions on the sender side
At least k messages have to be sent
Inefficient key discovery
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Also used in A key management scheme for distributed sensor networks
Instead of challenge response, submit the indexes
Less secure, as a smart attacker can easily find the nodes that have the key it wants
Key deployment II
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Method used in Establishing pair-wise keys forsecure communication in ad hoc networks: Aprobabilistic approach: A pool of P random keys is generated k indexes into the pool are created pseudo-
randomly with a publicly known seed dependent on the node id.
Less secure than challenge-response, but can be improved
Key deployment III
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Channel existence
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Find out which keys are shared and xor them together
An attacker needs to know all shared keys
Channel establishment
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Corruption probability – P=1000
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Corruption Probability – k=120
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The cooperative protocol
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Nearby sensors◦ Weaker against geographically attacks
Random◦ Larger communication overhead
Individual properties◦ More trusted nodes can give higher security
The C set
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They give an upper bound on the probability that the channel between two nodes is corrupted, given w corrupted nodes
Upper bound
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Sensor failure resistent◦ Can add more sensors if required
No information leakage◦ Sensors in the C set only transmits hash values of
their keys Adaptiveness
◦ If an upper bound of w is known, C can be chosen to secure communication with a desired probability.
Load balance◦ a sends c+1 message, sensors in C send 1,
tot=2c+1◦ Only done once during setup
Features of cooperation protocol
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Sensor doesn’t respond◦ After timeout, node a can pick another node
Sensor sends correct key◦ Lowers security
Sends false key◦ Can pick another C set◦ Notify trusted base-station◦ Aware that network is under attack
DoS Attacks of Malicious Cooperators
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If node a has the keys that node a should have, according to the pseudo-random number generator, it’s probable that a is a.
Authentication
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P=1000 and w=8
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P=1000 w=16
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P=10000 w=32
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M = {} for all keys k in P
◦ z = RND(id||k)◦ if(z%(|P|/m)==0)
put k into M
|M| must be less than memory size but larger than the security constraints
Discard ID if conditions not satisfied
Efficient and Secure Pre-deployment (ESP)
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Generated IDs
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Direct protocol