The proposed cryptographic model, VHCA, is a novel approach to encryption using cellular automata. This block cipher algorithm enables encryption and decryption of a plaintext using an arrangement of radius1 CA toggle rules, expressed as a binary secret key, to encrypt blocks having 128-bits or more. While hybrid CA forward evolution is used for encryption, a deterministic preimage computation logic is used for decryption. Promising results were obtained using periodic boundary condition, which favors diffusion, in combination with multiple permutive rules that are inherently balanced functions. Evaluations of the method using statistical randomness test suites, NIST and PractRand, point to the cryptographic robustness of VHCA.
Cellular automata (CAs) are homogeneous dynamical systems discrete in time, space and state variables, with global states being updated by means of a local function acting of the neighbourhood of their constituting parts. The family of elementary CAs (ECAs) is made up by the one-dimensional binary CAs with three next-nearest neighbours. Any one-dimensional CA's local function can be represented by a De Bruijn graph, in which connected pairs of nodes represent its possible neighbourhoods and the edges connecting them, the corresponding state transitions. De Bruijn graphs are specific kinds of process graphs, which are non-deterministic finite automata that can be used to represent the CA's regular language obtained at each finite instant of time in the CA's temporal evolution. The complexity of a process graph is defined defined in terms of the number of its nodes and edges. Previous works already analysed process graphs of ECAs' temporal evolution and their complexities, as well as their growth patterns over several iterations and limit behaviour. Here, we advance on what is known in this respect for ECAs, expanding previously known complexity data on the evolution of process graphs for various rules, inferring the limit behaviour of two rules and developing a direct way of constructing the process graph associated to a specific rule at any finite number of time steps.
Urban transport is a complex and dynamic system that affects the productivity, economy, and environment of cities. Traffic congestion and parking are two major challenges that urban transport faces, as they reduce the efficiency and capacity of the road network and cause delays and pollution. In this paper, we propose a novel system for traffic modeling and parking space management in urban centers, based on Cellular Automata (CAs). The system simulates the movement of vehicles on the road and allows drivers to find and reserve parking spaces in real time. Moreover, real data from the center of Alexandroupoli City in Greece have been used as a study case for the proposed system. The system incorporates various features to make the traffic model more realistic, such as intersections, traffic lights, multi-lane, parking procedure, and vehicle sizes. The paper demonstrates how the proposed system can prevent traffic congestion and, moreover, improve parking availability in urban areas.
A cellular automaton (CA) is a bio-inspired and parallel computing paradigm, whereby how to reduce the model's complexity but without compromising its computing power is a crucial subject. A typical example is the alpha-asynchronous cellular automaton (alpha-ACA) in (Lee. et al, 2005), which has the least complexity among all CAs of the same type and is able to implement a universal Turing machine, i.e., it is Turing- complete. The reduced complexity, however, comes at a cost that makes the ACA hard to realize the full functionalities of asynchronous circuits, especially of those circuits that can process an arbitrary number of signals in parallel. Such deficiency may raise a question about the parallel computing ability of the model. Because massive parallelism is an inherent feature of a CA and constitutes the basis for simulating various complex structures, including artificial intelligent systems and life, this paper attempts to identify a further universality of the alpha-ACA beyond the Turing-completeness. To this end, an effective scheme is proposed to explicitly construct a large-scale asynchronous circuit out of a restricted set of elements, which enables the ACA to simulate a universal synchronous cellular automaton via time-space rescaling, rather than a universal Turing machine. As a result, the alpha-ACA may possibly utilize its massive parallelism into universal computations as efficiently as other synchronous CAs or bio-inspired systems.
We propose a method for constructing 9-variable cryptographic Boolean functions from the iterates of 5-variable cellular automata rules. We then analyze, for important cryptographic properties of 5variable cellular automata rules, how they are preserved after extension to 9-variable Boolean functions. For each cryptographic property, we analyze the proportion of 5-variable cellular automata rules that preserve it for each of the 48 affine equivalence classes.
