This paper presents the design and implementation of an integrated architecture for key exchange and authentication in wireless sensor networks (WSNs) employing elliptic curve cryptography (ECC) for key management. Instead of implementing a standard algorithm such as SHA or AES for authentication, this paper considers an elliptic curve based message authentication code (MAC) for optimized design of overall structure through hardware reuse. The proposed architecture time shares the point multiplication unit between functionalities of key exchange and MAC there by reducing the structural complexity. The proposed architecture is implemented over GF(2 163 ) on a Kintex 7 FPGA board using Xilinx ISE. The EC point multiplication is done using Lopez-Dahab algorithm and the finite field elements are represented using Gaussian normal basis to reduce the computational complexity and resist side channel attack.

The resource constrained applications in the present day communication networks demand the use of new cryptographic protocols and hardware with reduced computational and structural complexity. The use of standard, standalone cryptographic primitives are not suitable for such applications. This paper proposes the implementation of a new integrated system for both encryption and authentication based on elliptic curves. An algorithm for pseudo random sequence generation based on cryptographic one way function of elliptic curve point multiplication is developed. This is combined with an elliptic curve based message authentication code to form the integrated system. EC point multiplication operation is preferred as cryptographic one way function for use in this system due to its high security per bit of the key. The hardware is implemented on a Virtex 5 FPGA using Xilinx ISE. In the proposed hardware implementation a single point multiplication unit is time shared between the operations of pseudo random sequence generation and authentication to reduce the overall hardware complexity. A comparison of the resource requirement of the proposed implementation with existing standalone methods is also done.

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