Sybil attack is a harmful threat to sensor networks, in which a malicious node illegally forges
an unbounded number of identities to defeat redundancy mechanisms. Digital certificates
are a way to prove identities. However, they are not viable in sensor networks. In this paper,
we propose a light-weight identity certificate method to defeat Sybil attacks. Our proposed
method uses one-way key chains and Merkle hash trees. The method thereby avoids the
need for public key cryptography. In addition, the method provides a means for …

A node B of a communication network receives a partial certificate from each of a plurality of
nodes A i in the communication network, constructs an identity certificate based on the
partial certificates received from the nodes A i, and transmits only a relevant part of the
identity certificate to any requesting node C in order to get its authenticity verified by the
node c.