10.2 Key management and distribution

Key management is crucial for securing wireless sensor networks. It involves generating, distributing, and updating encryption keys to protect data. Different methods like pre-distribution and pairwise establishment are used, each with pros and cons.

Effective key management ensures confidentiality and integrity in WSNs. It must balance security with resource constraints, adapting to network changes and threats. Proper implementation is vital for overall network security.

Key Cryptography Techniques

Symmetric Key Cryptography

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• Uses a single secret key for both encryption and decryption of data
• The same key is shared between the sender and receiver
• Provides confidentiality and authentication in WSNs
• Requires secure key distribution and management to prevent unauthorized access
• Computationally efficient compared to public key cryptography
• Examples of symmetric key algorithms include AES (Advanced Encryption Standard) and DES (Data Encryption Standard)

Public Key Cryptography

• Uses a pair of keys: a public key for encryption and a private key for decryption
• The public key is freely distributed, while the private key is kept secret by the owner
• Enables secure communication without the need for prior key sharing
• Provides confidentiality, authentication, and non-repudiation
• Computationally more expensive than symmetric key cryptography
• Suitable for key exchange and digital signatures in WSNs
• Examples of public key algorithms include RSA (Rivest-Shamir-Adleman) and ECC (Elliptic Curve Cryptography)

Key Distribution Methods

Key Pre-distribution

• Keys are loaded into sensor nodes before deployment
• Each node is pre-loaded with a set of keys from a large key pool
• Nodes can establish secure links with neighbors that share common keys
• Provides resilience against node capture attacks
• Suitable for static WSNs with known network topology
• Techniques include random key pre-distribution and deterministic key pre-distribution

Pairwise Key Establishment

• Enables two sensor nodes to establish a unique pairwise key for secure communication
• Can be achieved through key agreement protocols or key transport protocols
• Key agreement protocols allow nodes to derive a shared key without transmitting it over the network (Diffie-Hellman key exchange)
• Key transport protocols involve one node generating the key and securely transmitting it to the other node
• Provides better security compared to group keys, as compromised keys affect only the involved pair of nodes

Group Key Management

• Involves managing keys for secure group communication in WSNs
• A group key is shared among all members of a group for encrypting and decrypting group messages
• Efficient for broadcasting and multicasting in WSNs
• Requires mechanisms for group key generation, distribution, and updating
• Techniques include centralized group key management and distributed group key management
• Centralized approach relies on a key server to manage the group key, while distributed approach involves key agreement among group members

Hierarchical Key Management

• Organizes keys in a hierarchical structure based on the network topology
• Sensor nodes are divided into clusters, each managed by a cluster head
• Cluster heads form a higher-level network and communicate with the base station
• Different keys are used for intra-cluster and inter-cluster communication
• Reduces the overhead of key management and improves scalability
• Suitable for large-scale WSNs with multi-hop communication
• Techniques include LEAP (Localized Encryption and Authentication Protocol) and SHELL (Scalable, Hierarchical, Efficient, Location-aware, and Lightweight)

Key Management Operations

Key Revocation

• The process of invalidating and removing compromised or expired keys from the network
• Necessary to maintain the security of WSNs when nodes are captured, keys are leaked, or nodes are no longer trusted
• Involves revoking the keys associated with the compromised nodes and updating the keys of the remaining nodes
• Techniques include centralized key revocation and distributed key revocation
• Centralized approach relies on a key server to manage key revocation, while distributed approach involves collaborative decision-making among nodes

Key Refreshment

• The process of periodically updating keys to prevent cryptanalytic attacks and limit the impact of key compromise
• Helps to maintain the long-term security of WSNs
• Involves generating new keys and distributing them to the nodes in a secure manner
• Can be performed globally for the entire network or locally for specific nodes or clusters
• Techniques include time-based key refreshment and event-based key refreshment
• Time-based approach refreshes keys at regular intervals, while event-based approach refreshes keys upon detecting suspicious activities or node compromises