Secure Key Renewal and Revocation for Wireless Sensor Networks

Once a secure mechanism for authenticated communication is deployed in a Wireless Sensor Network (WSN), several situations may arise: a node can leave the network, a new node can join the network, an intruder could try to join the network or capture a node. Therefore it is important to revoke and renew certain keys that are learned by a malicious node. We propose several secure WSN protocols for revocations and renewal of cryptographic keys in the network based on symmetric encryption and elliptic curve cryptography (ECC). For all our solutions, we provide a formal analysis of the security of our protocols using Scyther, an automatic verification tool for cryptographic protocols. All the proposed protocols are proven secure but have different security levels by using different types of keys. Finally we implemented all our protocols on real testbeds using TelosB motes and compared their efficiency.