Public key cryptography in sensor networks-revisited

Abstract

The common perception of public key cryptography is that it is complex, slow and power hungry, and as such not at all suitable for use in ultra-low power environments like wireless sensor networks. It is therefore common practice to emulate the asymmetry of traditional public key based cryptographic services through a set of of protocols using symmetric key based message authentication codes (MACs). Although the low computational complexity of MACs is advantageous, the protocol layer requires time synchronization between devices on the network and a significant amount of overhead for communication and temporary storage. The requirement for a general purpose CPU to implement these protocols as well as their complexity makes them prone to vulnerabilities and practically eliminates all the advantages of using symmetric key techniques in the first place. In this paper we chanllenge the basic assumptions about public key cryptography in sensor networks which are based on a traditional software based approach. We propose a custom hardware asisted approach for which we claim that it makes public key cryptography ritms and associated parameters, careful optimization, and low-powerdesign techniques. In order to validate our claim we present proff of concept implementations of two different algorithms-Rabin's Scheme and NtruEncrypt-and analyze their architecture and performance according to various established metrics like power consumption, area, delay, throughput, level of security and energy per bit. Our implementation of NtruEncrypt in ASIC standard cell logic uses no more than 3,000 gates with an average power consumption of less than 20μW. We envision that our public key core would be embedded into a light-weight sensor node architecture.