Abstract—Sensor networks involving human participants will require privacy protection before wide deployment is feasible. This paper proposes and evaluates a set of protocols that enable anonymous data collection in a sensor network. Sensor nodes, instead of transmitting their actual data, transmit a sample of the data complement to a basestation. The basestation then uses the negative samples to reconstruct a histogram of the original sensor readings. These protocols, collectively defined as a negative survey, are computationally simple and do not increase communication overhead. Thus, the negative survey can be implemented efficiently on existing sensor network platforms. We analyze the accuracy of the negative survey under a variety of conditions and define a range of parameter values for which it is practical. We also describe an example traffic monitoring application that uses the negative survey to classify traffic behavior. We demonstrate that for reasonable traffic scenarios, the system accurately classifies traffic behavior without revealing private information. I.

Elliptic Curve Cryptography provides a secure means of exchanging keys among communicating hosts using the Diffie Hellman Key Exchange algorithm. Encryption and Decryption of texts and messages have also been attempted. This paper presents the implementation of ECC by first transforming the message into an affine point on the EC, and then applying the knapsack algorithm on ECC encrypted message over the finite field GF(p). In ECC we normally start with an affine point called Pm(x,y). This point lies on the elliptic curve. In this paper we have illustrated encryption/decryption involving the ASCII value of the characters constituting the message, and then subjecting it to the knapsack algorithm. We compare our proposed algorithm with RSA algorithm and show that our algorithm is better due to the high degree of sophistication and complexity involved. It is almost infeasible to attempt a brute force attack. Moreover only one parameter, namely the Knapsack vector ai alone needs to be kept secret. On the contrary in RSA, three parameters such as the modulus n, its factors p and q need to be kept secret.

In this paper the implementation of arithmetic operations in ECC is described.Elliptic curve cryptography is very useful in the field of the network security because of its small key size and its high strength of security.In this paper briefly describing general arithmetic operations we focus on scalar multiplication. We present two techniques: (i)reducing Hamming weight of scalars in binary representation and (ii) using sliding window, for obtatining scalar multiplication in a faster manner. Use of both the techniques is explained by suitable examples. General Terms Elliptic curve cryptography, scalar multiplication, wireless sensor, binary fields

Abstract. In this paper, we revisit a generally accepted opinion: implementing Elliptic Curve Cryptosystem (ECC) over GF (2 m) on sensor motes using small word size is not appropriate because XOR multiplication over GF (2 m) is not efficiently supported by current low-powered microprocessors. Although there are some implementations over GF (2 m) on sensor motes, their performances are not satisfactory enough to be used for wireless sensor networks (WSNs). We have found that a field multiplication over GF (2 m) are involved in a number of redundant memory accesses and its inefficiency is originated from this problem. Moreover, the field reduction process also requires many redundant memory accesses. Therefore, we propose some techniques for reducing unnecessary memory accesses. With the proposed strategies, the running time of field multiplication and reduction over GF (2 163) can be decreased by 21.1 % and 24.7%, respectively. These savings noticeably decrease execution times spent in Elliptic Curve Digital Signature Algorithm (ECDSA) operations