Software Implementation of P−adic Self−shrinking Generator for Aerospace Cryptographic Systems

To be suitable for use in aerospace cryptographic systems software-oriented stream ciphers must be fast, uniform, scalable, consistent and unpredictable. With regard in the paper the software implementation of a fast stream cipher, named Self−Shrinking p−adic Generator which produces 8 bits (SSPG-8) in one clock cycle, is proposed. The theoretical base of Self-Shrinking p-adic Generator is recalled. The software implementation of p-adic Self−Shrinking Generator is described. Analysis of more than 300 aerospace images is presented. The results from statistical analysis show that the sequence, generated by p-adic SSPG-8, is appropriate for a particular aerospace cryptographic application. INTRODUCTION The need of software-oriented stream ciphers in modern aerospace cryptographic systems has rapidly grown during the last several years. To be suitable for use in aerospace the stream ciphers must be fast, uniform, scalable, consistent and unpredictable. One of the most used cryptographic systems is the binary additive stream cipher in whitch the keystream, the plaintext and the ciphertext are basic binary sequences. The keystream is generated from a keystream generator, which takes a secret key as a seed, and produces a long pseudorandom sequence. The ciphertext is generated by bitwise modulo 2 additions of the keystream and the plaintext. The main goal of software-oriented stream cipher design is to generate efficient pseudorandom sequence [3], [4], [5] witх fast software algorithm and with truly random sequences properties. A fast software implementation of pseudo random number generator (PRNG), named Self−Shrinking p-adic Generator − 8 bits (SSPG−8), is proposed and an analysis of encrypted with SSPG−8 images is given in this paper. THE THEORETICAL BASICS OF SELF-SHRINKING P-ADIC GENERATOR In this section the theoretical basic of a recently proposed Self-Shrinking p−adic Generator (SSPG) [7] and some basic SSPG properties will be recalled. A. THE SSPG ARCHITECTURE In contrast with the classic self-shrinking generator [3] the SSPG architecture (Fig. 1) uses a p-adic FCSR instead of LFSR. This allows the generator to produce a number in the range 0 to p−1 in one step (ai = [0, 1, ..., p−1]). The self-shrinking p-adic generator selects a portion of the output p-adic FCSR sequence by controlling of the p-adic FCSR itself using the following algorithm.