Wireless sensor networks (WSNs) are composed of tiny devices with limited computation and battery capacities. For such resource-constrained devices, data transmission is a very energy-consuming operation. To maximize WSN lifetime, it is essential to minimize the number of bits sent and received by each device. One natural approach is to aggregate sensor data along the path from sensors to the sink. Aggregation is especially challenging if end-to-end privacy between sensors and the sink (or aggregate integrity) is required. In this article, we propose a simple and provably secure encryption scheme that allows efficient additive aggregation of encrypted data. Only one modular addition is necessary for ciphertext aggregation. The security of the scheme is based on the indistinguishability property of a pseudorandom function (PRF), a standard cryptographic primitive. We show that aggregation based on this scheme can be used to efficiently compute statistical values, such as mean, variance, and standard deviation of sensed data, while achieving significant bandwidth savings. To protect the integrity of the aggregated data, we construct an end-to-end aggregate authentication scheme that is secure against outsider-only attacks, also based on the indistinguishability property of PRFs.

Abstract-Key management is an essential cryptographic primitive upon which other security primitives are built. However, none of the existing key management schemes are suitable for ad hoc networks. They are either too inefficient, not functional on an arbitrary or unknown network topology, or not tolerant to a changing network topology or link failures. Recent research on distributed sensor networks suggests that key pre-distribution schemes (KPS) are the only practical option for scenarios where the network topology is not known prior to deployment. However, all of the existing KPS schemes rely on trusted third parties (TTP) rendering them inapplicable in many ad hoc networking scenarios and thus restricting them from wide-spread use in ad hoc networks. To eliminate this reliance on TTP, we introduce distributed key pre-distribution scheme (DKPS) and construct the first DKPS prototype to realize fully distributed and selforganized key pre-distribution without relying on any infrastructure support. DKPS overcomes the main limitations of the previous schemes, namely the needs of TTP and an established routing infrastructure. It minimizes the requirements posed on the underlying networks and can be easily applied to the ad hoc networking scenarios where key pre-distribution schemes were previously inapplicable. Finally, DKPS is robust to changing topology and broken links and can work before any routing infrastructure has been established, thus facilitating the widespread deployment of secure ad hoc networks.Keywords -distributed cryptographic protocol, key predistribution, ad hoc network, cover-free family, probabilistic method, privacy homomorphism.

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A formal treatment to the security of Concealed Data Aggregation (CDA) and the more general Private Data Aggregation (PDA) is given. While there exist a handful of constructions, rigorous security models and analyses for CDA or PDA are still lacking. Standard security notions for public key encryption, including semantic security and indistinguishability against chosen ciphertext attacks, are refined to cover the multisender nature and aggregation functionality of CDA and PDA in the security model. The proposed security model is sufficiently general to cover most application scenarios and constructions of privacy-preserving data aggregation. An impossibility result on achieving security against adaptive chosen ciphertext attacks in CDA/PDA is shown. A generic CDA construction based on public key homomorphic encryption is given, along with a proof of its security in the proposed model. The security of a number of existing schemes is analyzed in the proposed model.