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Cryptographic Algorithms on Reconfigurable Hardware- P8: This chapter presents a complete outhne for this Book. It explains the main goals pursued, the strategies chosen to achieve those goals, and a summary of the material to be covered throughout this Book. | 7 Reconfigurable Hardware Implementation of Hash Functions This Chapter has two main purposes. The first purpose is to introduce readers to how hash functions work. The second purpose is to study key aspects of hardware implementations of hash functions. To achieve those goals we selected MD5 as the most studied and widely used hash algorithm. A step-by-step description of MD5 has been provided which we hope will be useful for understanding the mathematical and logical operations involved in it. The study and analysis of MD5 will be utilized as a base for explaining the most recent SHA2 family of hash algorithms. We start this Chapter given a brief introduction to hash algorithms in Section 7.1. A survey of some famous hash algorithms is presented in Section 7.2. Then we provide a detailed discussion of the MD5 algorithm in Sec. 7.3. All MD5 steps are explained by means of an illustrative example which is explained at a bit level. In Section 7.4 we describe the SHA2 family of hash algorithms and some tips are provided with respect to their hardware implementation. In Section 7.5 design strategies to achieve efficient hash algorithms when implemented on reconfigurable devices are discussed. Section 7.6 presents a review of recent hash function hardware implementations. Finally in Section 7.7 concluding remarks are drawn. 7.1 Introduction As it was explained in Chapter 2 a Hash function H is a computationally efficient function that maps fixed binary chains of arbitrary length 0 1 to bit sequences H B of fixed length. H M is the hash value hash code or digest of M 110 . In words let M be a message of an arbitrary length. A hash function operates on Aiand returns a fixed-length value h as shown in Fig. 7.1. The value h is commonly called hash code. It is also referred to as a message Please purchase PDF Split-Merge on www.verypdf.com to remove this watermark. 190 7. Reconfigurable Hardware Implementation of Hash Functions digest or hash value. The main application of
