VerifyThis 2015 was a one-day program verification competition which took place on April 12th, 2015 in London, UK, as part of the European Joint Conferences on Theory and Practice of Software (ETAPS 2015). It was the fourth instalment in the VerifyThis competition series. This article provides an overview of the VerifyThis 2015 event, the challenges that were posed during the competition, and a high-level overview of the solutions to these challenges. It concludes with the results of the competition and some ideas and thoughts for future instalments of VerifyThis.

Pseudo-random number generators (PRNGs) are a critical infrastructure for cryptography and security of many computer applications. At the same time, PRNGs are surprisingly difficult to design, implement, and debug. This paper presents the first static analysis technique specifically for quality assurance of cryptographic PRNG implementations.

Regression verification and checking for illicit information flow in programs are probably the two most prominent instances of so-called relational program reasoning. Regression verification is concerned with proving that two programs behave either equally or differently in a formally specified manner; information-flow checking aims to establish that an attacker cannot distinguish executions of a program that vary in a part of the initial state designated as secret. While the theoretical connections between the two problems are well understood, there are also subtle but significant pragmatic differences. This paper reports the results of an experiment to adapt a state-of-the-art deductive information-flow verification system for Java to the problem of regression verification.

Automated machines and plants are operated for some decades and undergo an everlasting evolution during this time. In this paper, we present three related open evolution challenges focusing on software evolution in the domain of automated production systems, i.e. evolution and co-evolution of (interdisciplinary) engineering models and code, quality assurance as well as variant and version management during evolution.

Regression verification is an approach complementing regression testing with formal verification. The goal is to formally prove that two versions of a program behave either equally or differently in a precisely specified way. In this paper, we present a novel automatic approach for regression verification that reduces the equivalence of two related imperative integer programs to Horn constraints over uninterpreted predicates. Subsequently, state-of-the-art SMT solvers are used to solve the constraints. We have implemented the approach, and our experiments show non-trivial integer programs that can now be proved equivalent without further user input.

Abstract We present MODL, a Dynamic Logic and a deductive verification calculus for a core Java-like language that includes multi-threading. The calculus is based on symbolic execution. Even though we currently do not handle non-atomic loops, employing the technique of symmetry reduction allows us to verify systems without limits on state space or thread number. We have instantiated our logic for (restricted) multi-threaded Java programs and implemented the verification calculus within the KeY system. We demonstrate our approach by verifying a central method of the StringBuffer class from the Java standard library in the presence of unbounded concurrency.

In this paper, we present an approach aiming at full junctional deductive verification of concurrent Java programs, based on symbolic execution. We define a dynamic logic and a deductive verification calculus for a restricted fragment of Java with native concurrency primitives. Even though we cannot yet deal with non-atomic loops, employing the technique of symmetry reduction allows us to verify unbounded systems. The calculus has been implemented within the KeY system, and we demonstrate it by verifying a central method of the StringBuffer class from the Java standard library.