Randomness evaluation of coupled chaotic maps via NIST tests: A comparative study

Abstract

A vital requirement for any random number generator based on chaos is to ensure that the generated sequence always benefits of a significant level of randomness. It is critical to examine such sequences by means of Lyapunov exponents, bifur-cation diagrams, or other tests in order to accurately select the parameters of the dynamic system. However, the sequence’s randomness quality varies depending on the generator's design and must be examined in different ways. Therefore, we argue to use the National Institute of Standards and Technology (NIST) suite tests to evaluate and compare the randomness properties of two coupled systems found in existing literature: the logistic-sine system (LSS) and the logistic-tent system (LTS). The results reveal that the LSS has much superior statistical features in terms of randomness than the LTS in the range [3.1–4]. This conclusion will substantially affect the selection of the perfect chaotic map to create sequences of keys that match the requirements of cryptography applications.