Cryptographic Hash Functions and Attack Complexity Analysis

Abstract

A massive amount of sensitive data is currently being transferred with the meteoric rise in Internet of Things (IoT) applications. Images supplied by these applications are improving standards of living, providing high-end facilities to monitor critical issues in healthcare, agriculture, production industries, weather monitoring, smart cities, defence, underwater surveillance, and smart grid, among others. Typical IoT applications involve three layers: (1) a physical or perception layer which contains sensory devices; (2) a network layer containing networking devices such as gateways and routers to communicate data sensed by the sensors to the cloud servers; and (3) an application layer which has the necessary interface to interact with the end users. Sensory devices generally have constraints regarding computing capability, communication power, bandwidths, latency, and battery capacity. Therefore, providing secure communications between these devices is an exceedingly important criterion for various sensing applications. Any inadvertent security attack could be life-threatening for an individual, or could cause havoc for the entire nation. Conventional ciphers cannot be implemented due to their inherent complexities and high power consumption. Lightweight ciphers represent a possible security solution for the perception layer. However, the selection of tools to build a lightweight cipher is highly dependent on the type of sensory device being used for an application. This chapter describes the design of a lightweight cipher for the perception layer of IoT applications, using cellular automata (CA) for both text and image data. Since conventional CA-based ciphers lack the required resistance against many security attacks, the chapter first examines some basic requirements that satisfy the essential cryptographic criteria for building symmetric key block ciphers.