A survey of security issues in wireless sensor networks <s> CIPHER-BASED SECURE DATA AGGREGATION <s> End-to-end encryption for wireless sensor networks is a challenging problem. To save the overall energy resources of the network, it is agreed that sensed data need to be consolidated and aggregated on their way to the final destination. We present an approach that (1) conceals sensed data end-to-end, by (2) still providing efficient in-network data aggregation. The aggregating intermediate nodes are not required to operate on the sensed plaintext data. We apply a particular class of encryption transformation and exemplarily discuss the approach on the basis of two aggregation functions. We use actual implementation to show that the approach is feasible and flexible and frequently even more energy efficient than hop-by-hop encryption. <s> BIB001 </s> A survey of security issues in wireless sensor networks <s> CIPHER-BASED SECURE DATA AGGREGATION <s> Wireless sensor networks (WSNs) are ad-hoc networks composed of tiny devices with limited computation and energy capacities. For such devices, data transmission is a very energy-consuming operation. It thus becomes essential to the lifetime of a WSN to minimize the number of bits sent by each device. One well-known approach is to aggregate sensor data (e.g., by adding) along the path from sensors to the sink. Aggregation becomes especially challenging if end-to-end privacy between sensors and the sink is required. In this paper, we propose a simple and provably secure additively homomorphic stream cipher that allows efficient aggregation of encrypted data. The new cipher only uses modular additions (with very small moduli) and is therefore very well suited for CPU-constrained devices. We show that aggregation based on this cipher can be used to efficiently compute statistical values such as mean, variance and standard deviation of sensed data, while achieving significant bandwidth gain. <s> BIB002 </s> A survey of security issues in wireless sensor networks <s> CIPHER-BASED SECURE DATA AGGREGATION <s> In sensor networks, data aggregation is a vital primitive enabling efficient data queries. An on-site aggregator device collects data from sensor nodes and produces a condensed summary which is forwarded to the off-site querier, thus reducing the communication cost of the query. Since the aggregator is on-site, it is vulnerable to physical compromise attacks. A compromised aggregator may report false aggregation results. Hence, it is essential that techniques are available to allow the querier to verify the integrity of the result returned by the aggregator node. ::: ::: We propose a novel framework for secure information aggregation in sensor networks. By constructing efficient random sampling mechanisms and interactive proofs, we enable the querier to verify that the answer given by the aggregator is a good approximation of the true value, even when the aggregator and a fraction of the sensor nodes are corrupted. In particular, we present efficient protocols for secure computation of the median and average of the measurements, for the estimation of the network size, for finding the minimum and maximum sensor reading, and for random sampling and leader election. Our protocols require only sublinear communication between the aggregator and the user. <s> BIB003
Two cipher-based secure data aggregation schemes were proposed in BIB001 BIB002 , works which are based on a particular encryption transformation called a privacy homomorphism (PH). This is an encryption transformation that allows direct computation on encrypted data. Let Q and R denote two rings, and let + denote addition and × denote multiplication on both. Let K be the key space. We denote an encryption transformation E: K × Q → R and the corresponding decryption transformation D : K × R → Q. Given a, b ∈ Q, and k ∈ K, we term additively homomorphic and multiplicative homomorphic  . The proposed scheme in BIB001 , Concealed Data Aggregation (CDA), is based on the PH proposed in  , although the study in  has shown that the proposed PH in  is unsecure against chosen plain text attacks for some parameter settings. In BIB001 the authors claimed that, for the WSN data aggregation scenario, the security level is still adequate and the proposed PH method in  can be employed for encryption. CDA can be used to calculate SUM and AVERAGE in a hierarchical WSN. To calculate AVERAGE, an aggregator needs to know the number of sensor nodes n. Castelluccia et al. proposed a simple and provable secure additively homomorphic stream cipher (HSC) that allows for the efficient aggregation of encrypted data BIB002 . The new cipher uses modular addition and is therefore very well suited for CPU-constrained devices such as those in WSNs. The aggregation based on this cipher can be used to efficiently compute statistical values such as the mean, variance, and standard deviation of sensed data while achieving significant bandwidth gain. BIB003 ).