Timed Automaton-Based Quantitative Feasibility Analysis of Symmetric Cipher in Embedded RTOS: A Case Study of AES

The real-time operating system (RTOS) has a wide range of application domains and provides devices with the ability to schedule resources. Because of the restricted resources of embedded devices and the real-time constraints of RTOS, the application of cryptographic algorithms in these devices will affect the running systems. The existing approaches for RTOS ciphers’ evaluation are mainly provided by experimental data performance analysis, which, however, lack a clear judgment on the affected RTOS performance indicators, such as task schedulability, bandwidth, as well as a quantitative prediction of the remaining resources of RTOS. By focusing on task schedulability in RTOS, this paper provides a timed automaton-based quantitative approach to judge the feasibility of ciphers in embedded RTOS. First, a cryptographic algorithm execution overhead estimation model is established. Then, by combining the overhead model with a sensitivity analysis method, we can analyze the feasibility of the cryptographic algorithm. Finally, a task-oriented and timed automaton-based model is built to verify the analysis results. We take AES as a case study and carry out experiments on embedded devices. The experimental results show the effectiveness of our approach, which will provide specific feasibility indicators for the application of cryptographic algorithms in RTOS.

Transforming Robotic Plans with Timed Automata to Solve Temporal Platform Constraints

Task planning for mobile robots typically uses an abstract planning domain that ignores the low-level details of the specific robot platform. Therefore, executing a plan on an actual robot often requires additional steps to deal with the specifics of the robot platform. Such a platform can be modeled with timed automata and a set of temporal constraints that need to be satisfied during execution. In this paper, we describe how to transform an abstract plan into a platform-specific action sequence that satisfies all platform constraints. The transformation procedure first transforms the plan into a timed automaton, which is then combined with the platform automata while removing all transitions that violate any constraint. We then apply reachability analysis on the resulting automaton. From any solution trace one can obtain the abstract plan extended by additional platform actions such that all platform constraints are satisfied. We describe the transformation procedure in detail and provide an evaluation in two real-world robotics scenarios.

Timed Bounded Verification of Inclusion Based on Timed Bounded Discretized Language

The inclusion problem is one of the common problems in real-time systems. The general form of this problem is undecidable; however, the time-bounded verification of inclusion problem is decidable for timed automata. In this study, we propose a new discretization technique to verify the inclusion problem. The proposed technique is applied to a non-Zeno timed automaton with an upper bound that does not contain a non-reachable space for each transition. The new approach is based on the generation of timed bounded discretized language that represents an abstraction of timed words in the form of a set of a countable number of discrete timed words. A discrete timed word aggregates all timed words that share the same actions and their execution times that create the time continuous intervals. The lower and the upper bounds of an interval in a discrete timed word is defined by the minimum and maximum execution times associated to a given transition-run. In addition, we propose the verification schema of the inclusion between two timed bounded discretized languages generated by two non-Zeno timed automata.

Iterative Bounded Synthesis for Efficient Cycle Detection in Parametric Timed Automata

We study semi-algorithms to synthesise the constraints under which a Parametric Timed Automaton satisfies some liveness requirement. The algorithms traverse a possibly infinite parametric zone graph, searching for accepting cycles. We provide new search and pruning algorithms, leading to successful termination for many examples. We demonstrate the success and efficiency of these algorithms on a benchmark. We also illustrate parameter synthesis for the classical Bounded Retransmission Protocol. Finally, we introduce a new notion of completeness in the limit, to investigate if an algorithm enumerates all solutions.

Exact acceleration of complex real-time model checking based on overlapping cycle

When real-time systems are modeled as timed automata, different time scales may lead to substantial fragmentation of the symbolic state space. Exact acceleration solves the fragmentation problem without changing system reachability. The relatively mature technology of exact acceleration has been used with an appended cycle or a parking cycle, which can be applied to the calculation of a single acceleratable cycle model. Using these two technologies to develop a complex real-time model requires additional states and consumes a large amount of time cost, thereby influencing acceleration efficiency. In this paper, a complex real-time exact acceleration method based on an overlapping cycle is proposed, which is an application scenario extension of the parking-cycle technique. By comprehensively analyzing the accelerating impacts of multiple acceleratable cycles, it is only necessary to add a single overlapping period with a fixed length without relying on the windows of acceleratable cycles. Experimental results show that the proposed timed automaton model is simple and effectively decreases the time costs of exact acceleration. For the complex real-time system model, the method based on an overlapping cycle can accelerate the large scale and concurrent states which cannot be solved by the original exact acceleration theory.

A Formal Approach To Validate Block-Chains

Our goal is to propose a suitable approach for validating blockchains. For this purpose, we intend to adopt formal methods which are based on strong mathematical foundations. More precisely, we follow a model-based testing approach. The latter consists in describing the behavior of the system using a specific formalism, deriving test cases from the obtained model and then executing the obtained tests on the implementation to check whether it is correct or not. The adopted formalism corresponds to the timed automaton Model. The generated tests may be either digital or analog. Moreover, we propose several techniques which allow to solve the state explosion which may be encountered during the verification and test generation phases.

A Formal Approach To Validate Block-Chains

Our goal is to propose a suitable approach for validating blockchains. For this purpose, we intend to adopt formal methods which are based on strong mathematical foundations. More precisely, we follow a model-based testing approach. The latter consists in describing the behavior of the system using a specific formalism, deriving test cases from the obtained model and then executing the obtained tests on the implementation to check whether it is correct or not. The adopted formalism corresponds to the timed automaton Model. The generated tests may be either digital or analog. Moreover, we propose several techniques which allow to solve the state explosion which may be encountered during the verification and test generation phases.