Danny Bøgsted Poulsen

Aalborg University · Department of Computer Science

Tools and techniques for assessing the possibilities and impacts of attacks on IT systems are necessary to ensure the IT systems upon which society depends on continue to operate despite targeted attacks. This reality compels the development of intuitive brainstorming formalisms like attack-defense trees. With an attack-defense tree and a suitable...

The prevalence of string solvers in formal program analysis has led to an increasing demand for more effective and dependable solving techniques. However, solving the satisfiability problem of string constraints, which is a generally undecidable problem, requires a deep understanding of the structure of the constraints. To address this challenge, t...

In this work investigate the use of stochastic hybrid models, statistical model checking and machine learning to analyze, predict and control the rapid spreading of Covid-19. During the pandemic numerous studies using stochastic models have been produced. Most of these studies are used to predict the effect of some restrictions. In contrast, in thi...

Statistical Model Checking is a simulations-based verification technique that has gathered increased focus in the past ten years, due to its applicability to handle much larger models compared to exhaustive verification techniques used in model checking. Statistical Model Checking is also applicable to a larger class of systems than exhaustive meth...

Many security-related properties—such as non-interference—cannot be captured by traditional trace-based specification formalisms such as LTL. The reason is that they relate the events of two (or more) traces of the system, and LTL can only reason on one execution at a time. A number of hyper-property extensions of LTL have been proposed in the past...

String solvers gained a more prominent role in the formal analysis of string-heavy programs, causing an ever-growing need for efficient and reliable solving algorithms. Regular constraints play a central role in several real-world queries. To emerge this field, we present two approaches to encode regular constraints as a Boolean satisfiability prob...

String constraint solving, and the underlying theory of word equations, are highly interesting research topics both for practitioners and theoreticians working in the wide area of satisfiability modulo theories. As string constraint solving algorithms, a.k.a. string solvers, gained a more prominent role in the formal analysis of string-heavy progra...

Path planning and task scheduling are two challenging problems in the design of multiple autonomous agents. Both problems can be solved by the use of exhaustive search techniques such as model checking and algorithmic game theory. However, model checking suffers from the infamous state-space explosion problem that makes it inefficient at solving th...

We perform a preliminary security analysis of the initial boot stage for the OpenTitan silicon root of trust, including formalisation and verification of relevant security goals using both bounded model checking and (unbounded) model checking. We further report on a potential vulnerability in the platform and show how it can be reproduced using for...

The increased interest in string solving in the recent years has made it very hard to identify the right tool to address a particular user's purpose. Firstly, there is a multitude of string solvers, each addressing essentially some subset of the general problem. Generally, the addressed fragments are relevant and well motivated, but the lack of com...

In recent years there has been a considerable effort in optimising formal methods for application to code. This has been driven by tools such as CPAChecker, DIVINE, and CBMC. At the same time tools such as Uppaal have been massively expanding the realm of more traditional model checking technologies to include strategy synthesis algorithms - an asp...

In recent years there has been a considerable effort in optimising formal methods for application to code. This has been driven by tools such as CPAChecker, Divine, and CBMC. At the same time tools such as Uppaal have been massively expanding the realm of more traditional model checking technologies to include strategy synthesis algorithms -- an as...

The Attack Defense Tree framework was developed to facilitate abstract reasoning about security issues of complex systems. As such, a zoo of techniques and extensions have emerged in an attempt to extend the simple Boolean logic of Attack Defense Trees with behavioral properties and quantities. In this paper we expand the modeling power of Attack D...

During the spring of 2020, the BEOCOVID project has been funded to investigate the use of stochastic hybrid models, statistical model checking and machine learning to analyse, predict and control the rapid spreading of Covid-19 . In this paper we focus on the SEIHR epidemiological model instance of Covid-19 pandemics and show how the risk of viral...

In this work we present our work in developing a software verification tool for llvm-code - Lodin - that incorporates both explicit-state model checking, statistical model checking and symbolic state model checking algorithms.

Prefix normal words are binary words in which each prefix has at least the same number of s as any factor of the same length. Firstly introduced in 2011, the problem of determining the index (amount of equivalence classes for a given word length) of the prefix normal equivalence relation is still open. In this paper, we investigate two aspects of t...

We present Woorpje, a string solver for bounded word equations (i.e., equations where the length of each variable is upper bounded by a given integer). Our algorithm works by reformulating the satisfiability of bounded word equations as a reachability problem for nondeterministic finite automata, and then carefully encoding this as a propositional...

We present Woorpje, a string solver for bounded word equations (i.e., equations where the length of each variable is upper bounded by a given integer). Our algorithm works by reformulating the satisfiability of bounded word equations as a reachability problem for nondeterministic finite automata, and then carefully encoding this as a propositional...

We present the new tool Lodin for statistical model checking of LLVM-bitcode. Lodin implements a simulation engine for LLVM-bitcode and implements classic statistical model checking algorithms on top of it. The simulation engine implements only the core of LLVM but supports extending this core through a plugin-architecture. Besides the statistical...

Metric Temporal Logic MTL0,∞ is a timed extension of linear temporal logic, LTL, with time intervals whose left endpoints are zero or whose right endpoints are infinity. Whereas the satisfiability and model-checking problems for MTL0,∞ are both decidable, we note that the controller synthesis problem for MTL0,∞ is unfortunately undecidable. A...

We present an importance sampling framework that combines symbolic analysis and simulation to estimate the probability of rare reachability properties in stochastic timed automata. By means of symbolic exploration, our framework first identifies states that cannot reach the goal. A state-wise change of measure is then applied on-the-fly during simu...

Performing a thorough security risk assessment of an organisation has always been challenging, but with the increased reliance on outsourced and off-site third-party services, i.e., “cloud services”, combined with internal (legacy) IT-infrastructure and -services, it has become a very difficult and time-consuming task. One of the traditional tools...

This tutorial paper surveys the main features of Uppaal SMC, a model checking approach in Uppaal family that allows us to reason on networks of complex real-timed systems with a stochastic semantic. We demonstrate the modeling features of the tool, new verification algorithms and ways of applying them to potentially complex case studies.

Statistical Model Checking (SMC) is a highly scalable simulation-based verification approach for testing and estimating the probability that a stochastic system satisfies a given linear temporal property. The technique has been applied to (discrete and continuous time) Markov chains, stochastic timed automata and most recently hybrid systems using...

In this paper we present a modelling formalism for dynamic networks of stochastic hybrid automata. In particular, our formalism is based on primitives for the dynamic creation and termination of hybrid automata components during the execution of a system. In this way we allow for natural modelling of concepts such as multiple threads found in vario...

We present a new technique for verifying Weighted Metric Temporal Logic (WMTL) properties of Weighted Timed Automata. Our approach relies on Statistical Model Checking combined with a new mon-itoring algorithm based on rewriting rules. Contrary to existing mon-itoring approaches for WMTL ours is exact. The technique has been implemented in the stat...

Complex computational systems are ubiquitous and their study increasingly important. Given the ease with which it is possible to construct large systems with heterogeneous technology, there is strong motivation to provide automated means to verify their safety, efficiency and reliability. In another context, biological systems are supreme examples...

This paper presents novel extensions and applications of the UPPAAL-SMC model checker. The extensions allow for statistical model checking of stochastic hybrid systems. We show how our race-based stochastic semantics extends to networks of hybrid systems, and indicate the integration technique applied for implementing this semantics in the UPPAAL-S...

This paper offers a survey of uppaalsmc, a major extension of the real-time verification tool uppaal. uppaalsmc allows for the efficient analysis of performance properties of networks of priced timed automata under a natural stochastic semantics. In particular, uppaalsmc relies on a series of extensions of the statistical model checking approach ge...

In this paper we propose a general framework for distributed statistical model checking of networks of priced timed automata. The first contribution is a new algorithm to distribute sequential hypothesis testing without introducing bias in the results. The second contribution is an implementation of this algorithm in Uppaal. The major contribution...

We present a novel approach and implementation for analysing weighted timed automata (WTA) with respect to the weighted metric temporal logic (WMTL≤). Based on a stochastic semantics of WTAs, we apply statistical model checking (SMC) to estimate and test probabilities of satisfaction with desired levels of confidence. Our approach consists in gener...

This paper offers a natural stochastic semantics of Networks of Priced Timed Automata (NPTA) based on races between components. The semantics provides the basis for satisfaction of probabilistic Weighted CTL properties (PWCTL), conservatively extending the classical satisfaction of timed automata with respect to TCTL. In particular the extension al...

Duration Probabilistic Automata (DPA) is a formal-ism for modelling concurrent execution of sequences of tasks. This formalism is well suited for schedul-ing problems such as job shop. We show how DPAs can be translated to other formalisms and how sta-tistical modelchecking can be applied. The perfor-mance of these translations is tested using the...

This paper offers a natural stochastic semantics of Networks of Priced Timed Automata (NPTA) based on races between components. The semantics provides the basis for satisfaction of Probabilistic Weighted CTL properties (PWCTL), conservatively extending the classical satisfaction of timed automata with respect to TCTL. In particular the extension al...