  Resource and cost constraints remain a challenge for wireless sensor network
security. In this paper, we propose a new approach to protect confidentiality
against a parasitic adversary, which seeks to exploit sensor networks by
obtaining measurements in an unauthorized way. Our low-complexity solution,
GossiCrypt, leverages on the large scale of sensor networks to protect
confidentiality efficiently and effectively. GossiCrypt protects data by
symmetric key encryption at their source nodes and re-encryption at a randomly
chosen subset of nodes en route to the sink. Furthermore, it employs key
refreshing to mitigate the physical compromise of cryptographic keys. We
validate GossiCrypt analytically and with simulations, showing it protects data
confidentiality with probability almost one. Moreover, compared with a system
that uses public-key data encryption, the energy consumption of GossiCrypt is
one to three orders of magnitude lower.
