Security Issues In Sensor Networks By Priya Palanivelu

What Is A Sensor Network ? A network is formed when a set of small sensor devices that are deployed in an ad hoc fashion cooperate for sensing a physical phenomenon.

Typical application of sensor networks Military sensor networks to detect enemy movements, the presence of hazardous material (such as poison gases or radiation, explosions, etc.) Environmental sensor networks (such as in plains or deserts or on mountains or ocean surfaces) to detect and monitor environmental changes. Wireless traffic sensor networks to monitor vehicle traffic on a highway or in a congested part of a city. Wireless surveillance sensor networks for providing security in a shopping mall, parking garage, or other facility.

Communication Architecture The sensor nodes communicate using RF The sensor nodes establish a routing forest, with a base station at the root of every tree Periodic transmission of beacons allows nodes to create a routing topology. The base station accesses individual nodes using source routing.

Challenges Of Sensor Network Energy consumption primarily – By radio communication – Need to minimize communication overhead Reliance on asymmetric digital signature – Long signatures with high communication overhead of bytes per packet – Very high overhead to create & verify signature “Symmetric broadcast authentication is impractical

Requirements for sensor networks security Data Confidentiality – From the observed communication pattern set up secure channels between nodes and base stations Data Authentication – Construct authenticated broadcast from symmetric primitives only – Introduce asymmetry with delayed key disclosure and one way function key chains Data Integrity Data Freshness – Recent data – No replay of data

Communication Pattern Of The Sensor Network 1) Node to base station communication, e.g. sensor readings. 2) Base station to node communication, e.g. specific requests. 3) Base station to all nodes, e.g. routing beacons, queries or reprogramming of the entire network.

security building blocks optimized for source constrained environments and wireless communication. SPINS _TESLA SNEP Timed, Efficient, Streaming, Loss-tolerant Authentication Protocol), Secure Network Encryption Protocol SPINS: Security Protocols for Sensor Networks

Important Baseline Security Primitives SNEP  Data confidentiality, two-party data authentication, and data freshness µTESLA  new protocol which provides authenticated broadcast for severely resource-constrained environments.

SNEP: Data Confidentiality, Authentication, Integrity, and Freshness Low communication overhead Adds only 8 bytes per message Uses counter Counter value is kept at both end points Provides semantic security – Prevents eavesdroppers from interfering the message content from the encrypted message Data authentication, replay protection, and weak/strong message freshness

SNEP-mechanism Communicating parties share a counter, which is used as an Initialization Vector (IV) Counter is not sent with the message Block ciphers are in Counter Mode (CTR) Counter incremented after each block MAC used to achieve 2 party data authentication and data integrity Counter value is never repeated Counter value in MAC prevents replay attacks

TESLA vs. µTESLA TESLA – Authenticates initial packet with a digital signature – Too expensive for sensor nodes – Disclosing a key in each packet requires too much energy(24bytes/packet) – Expensive to store one-way key chain µTESLA – Uses symmetric mechanism – Discloses key once every epoch – Restricts number of authenticated senders

µTESLA Overview Base station (BS) broadcasts authenticated information to nodes BS and nodes are loosely time synchronized Each node knows the upper bound on max. synchronization error BS computes a MAC on the packet The key is secret at this point Sensor receives the packet & stores it in buffer BS broadcasts the verification key to all receivers Node verifies the authenticity of the key Node uses key to authenticate the packet in the buffer

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