Sebastian Burg

Creating industrial-like SAT instances by clustering and reconstruction

For the optimization of SAT solvers, it is crucial that a solver can be trained on a preferably large number of instances for general or domain specific problems. Especially for domain specific problems the set of available instances can be insufficiently small. In our approach we built large sets of instances by recombining several small snippets of different instances of a particular domain. Also the fuzzer utility [3] builds industrial-like SAT instances by combining smaller pieces. However, these pieces are a combination of randomly created circuits and are not derived from an existing pool of instances. In Ansotegui [1] random pseudo-industrial instances are created in a more formal way.

Accelerated model-based robustness testing of state machine implementations

In this paper, we present an approach for accelerating model-based robustness testing of state-based software components. We use the Z3 SAT solver to derive executable test cases fully automatically from a state model based on a UML Statechart. The test cases are paths along the Statechart comprising states and transitions. The main advantage of our approach is an accelerated execution of the test cases by refining already reached states as starting points for further test cases using reverse execution. Furthermore, the presented approach is able to check whether a correct target state has been reached or not when executing the path-based test cases using runtime verification and therefore increases the test significance. The runtime verification is done without instrumenting the source code of the component under test.

Efficient Testing of Different Loop Paths

Loops can represent an infinite number of possible execution paths and therefore purse a major challenge for current static analysis frameworks and test input generators. In this paper, we introduce a new loop exploration algorithm to examine different iteration orders (i.e. loop paths) in order to test distinct loop behaviour. To reduce the complexity of testing all possible combinations of iterations, we introduce a criterion to group different paths into equivalence classes and show how to specifically generate test cases that cover the different equivalence classes. We demonstrate how this approach helps to achieve higher coverage rates and helps to find software failures that are not discovered by current test case generation frameworks.

End-to-Display Encryption: A Pixel-Domain Encryption with Security Benefit

Providing secure access to confidential information is extremely difficult, notably when regarding weak endpoints and users. With the increasing number of corporate espionage cases and data leaks, a usable approach enhancing the security of data on endpoints is needed. In this paper we present our implementation for providing a new level of security for confidential documents that are viewed on a display. We call this End-to-Display Encryption (E2DE). E2DE encrypts images in the pixel-domain before transmitting them to the user. These images can then be displayed by arbitrary image viewers and are sent to the display. On the way to the display, the data stream is analyzed and the encrypted pixels are decrypted depending on a private key stored on a chip card inserted in the receiver, creating a viewable representation of the confidential data on the display, without decrypting the information on the computer itself. We implemented a prototype on a Digilent Atlys FPGA Board supporting resolutions up to Full HD.

More Flexible Object Invariants with Less Specification Overhead

Object invariants are used to specify valid object states. They play a central role for reasoning about the correctness of object-oriented software. Current verification methodologies require additional specifications to support the flexibility of modern object oriented programming concepts. This increases the specification effort and represents a new source of error. The presented methodology reduces the currently required specification overhead. It is based on an automatic control flow analysis between code positions violating invariants and code positions requiring their validity. This analysis helps to prevent specification errors, possible in other approaches. Furthermore, the presented methodology distinguishes between valid and invalid invariants within one object. This allows a (more) flexible definition of invariants.

Linebased end-to-display encryption for secure documents

To protect data against theft from Trojan horses, some of the common approaches like End-to-End Encryption fail to counter such malicious attempts as they do not account for vulnerabilities of the users endpoint. Any data which is decrypted on the endpoint, can become visible to attackers. A technique that can prevent this dataloss is by employing encryption in the pixel-domain and using additional hardware to decrypt the graphics-stream. This is done by End-to-Display Encryption, which decrypts the data between the endpoint and the display, ensuring that the data-at-rest is always encrypted. In this paper, we present a linebased encryption method for a more user-friendly and improved End-to-Display Encryption design, which can be used to effectively counter corporate espionage by providing secure access to confidential documents.