Understanding Cutting Planes for QBFs

We define a cutting planes system CP+8red for quantified Boolean formulas (QBF) and analyse the proof-theoretic strength of this new calculus. While in the propositional case, Cutting Planes is of intermediate strength between resolution and Frege, our findings here show that the situation in QBF is slightly more complex: while CP+8red is again weaker than QBF Frege and stronger than the CDCL-based QBF resolution systems Q-Res and QU-Res, it turns out to be incomparable to even the weakest expansion-based QBF resolution system 8Exp+Res. Technically, our results establish the effectiveness of two lower boun

Contract Machines: An Engineer-friendly Specification Language for Mode-Based Systems

The first step in developing safe and functioning systems is the specification of the intended behavior. The development, validation, and verification depend on clear and unambiguous specifications. Building understandable specification tools requires adequate formalisms and representation to express the expected functional behavior. We present contract machines: a graphical specification language based on the well-known modeling concept of state machines and the intuitive semantics of assume-guarantee contracts. Contract machines (CMs) build upon the logical foundation of contract automata (CA) which are non-deterministic finite automata over alphabets of contracts, and provide the formal semantics of CMs. CAs can be processed by (semi-)automated verification and validation tools, such as model checkers or test case generators. In contrast to contract automata, contract machines offer a more high-level view of the system under scrutiny by providing more features to ease usability. We present features for effective controlling of non-determinism, using recurring specification patterns, e.g.\ for fault modes and error recovery behavior, and handling different versions and variants of systems

Frege systems for quantified Boolean logic

We define and investigate Frege systems for quantified Boolean formulas (QBF). For these new proof systems, we develop a lower bound technique that directly lifts circuit lower bounds for a circuit class C to the QBF Frege system operating with lines from C. Such a direct transfer from circuit to proof complexity lower bounds has often been postulated for propositional systems but had not been formally established in such generality for any proof systems prior to this work. This leads to strong lower bounds for restricted versions of QBF Frege, in particular an exponential lower bound for QBF Frege systems operating with AC0[p] circuits. In contrast, any non-trivial lower bound for propositional AC0[p]-Frege constitutes a major open problem. Improving these lower bounds to unrestricted QBF Frege tightly corresponds to the major problems in circuit complexity and propositional proof complexity. In particular, proving a lower bound for QBF Frege systems operating with arbitrary P/poly circuits is equivalent to either showing a lower bound for P/poly or for propositional extended Frege (which operates with P/poly circuits). We also compare our new QBF Frege systems to standard sequent calculi for QBF and establish a correspondence to intuitionistic bounded arithmetic.This research was supported by grant nos. 48138 and 60842 from the John Templeton Foundation, EPSRC grant EP/L024233/1, and a Doctoral Prize Fellowship from EPSRC (third author). The second author was funded by the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007–2013)/ERC grant agreement no. 279611 and under the European Union’s Horizon 2020 Research and Innovation Programme/ERC grant agreement no. 648276 AUTAR. The fourth author was supported by the Austrian Science Fund (FWF) under project number P28699 and by the European Research Council under the European Union’s Seventh Framework Programme (FP7/2007-2014)/ERC Grant Agreement no. 61507. Part of this work was done when Beyersdorff and Pich were at the University of Leeds and Bonacina at Sapienza University Rome.Peer ReviewedPostprint (published version

Data Fingerprinting -- Identifying Files and Tables with Hashing Schemes

Master's thesis in Computer scienceINTRODUCTION: Although hash functions are nothing new, these are not limited to cryptographic purposes. One important field is data fingerprinting. Here, the purpose is to generate a digest which serves as a fingerprint (or a license plate) that uniquely identifies a file. More recently, fuzzy fingerprinting schemes — which will scrap the avalanche effect in favour of detecting local changes — has hit the spotlight. The main purpose of this project is to find ways to classify text tables, and discover where potential changes or inconsitencies have happened. METHODS: Large parts of this report can be considered applied discrete mathematics — and finite fields and combinatorics have played an important part. Rabin’s fingerprinting scheme was tested extensively and compared against existing cryptographic algorithms, CRC and FNV. Moreover, a self-designed fuzzy hashing algorithm with the preliminary name No-Frills Hash has been created and tested against Nilsimsa and Spamsum. NFHash is based on Mersenne primes, and uses a sliding window to create a fuzzy hash. Futhermore, the usefullness of lookup tables (with partial seeds) were also explored. The fuzzy hashing algorithm has also been combined with a k-NN classifier to get an overview over it’s ability to classify files. In addition to NFHash, Bloom filters combined with Merkle Trees have been the most important part of this report. This combination will allow a user to see where a change was made, despite the fact that hash functions are one-way. Large parts of this project has dealt with the study of other open-source libraries and applications, such as Cassandra and SSDeep — as well as how bitcoins work. Optimizations have played a crucial role as well; different approaches to a problem might lead to the same solution, but resource consumption can be very different. RESULTS: The results have shown that the Merkle Tree-based approach can track changes to a table very quickly and efficiently, due to it being conservative when it comes to CPU resources. Moreover, the self-designed algorithm NFHash also does well in terms of file classification when it is coupled with a k-NN classifyer. CONCLUSION: Hash functions refers to a very diverse set of algorithms, and not just algorithms that serve a limited purpose. Fuzzy Fingerprinting Schemes can still be considered to be at their infant stage, but a lot has still happened the last ten years. This project has introduced two new ways to create and compare hashes that can be compared to similar, yet not necessarily identical files — or to detect if (and to what extent) a file was changed. Note that the algorithms presented here should be considered prototypes, and still might need some large scale testing to sort out potential flaw

Lower bounds: from circuits to QBF proof systems

A general and long-standing belief in the proof complexity community asserts that there is a close connection between progress in lower bounds for Boolean circuits and progress in proof size lower bounds for strong propositional proof systems. Although there are famous examples where a transfer from ideas and techniques from circuit complexity to proof complexity has been effective, a formal connection between the two areas has never been established so far. Here we provide such a formal relation between lower bounds for circuit classes and lower bounds for Frege systems for quantified Boolean formulas (QBF). Starting from a propositional proof system P we exhibit a general method how to obtain a QBF proof system P+∀red{P}, which is inspired by the transition from resolution to Q-resolution. For us the most important case is a new and natural hierarchy of QBF Frege systems C-Frege+∀red that parallels the well-studied propositional hierarchy of C-Frege systems, where lines in proofs are restricted to belong to a circuit class C. Building on earlier work for resolution [Beyersdorff, Chew and Janota, 2015a] we establish a lower bound technique via strategy extraction that transfers arbitrary lower bounds for the circuit class C to lower bounds in C-Frege+∀red. By using the full spectrum of state-of-the-art circuit lower bounds, our new lower bound method leads to very strong lower bounds for QBF \FREGE systems: 1. exponential lower bounds and separations for the QBF proof system ACo[p]-Frege+∀red for all primes p; 2. an exponential separation of ACo[p]-Frege+∀red from TCo/d-Frege+∀red; 3. an exponential separation of the hierarchy of constant-depth systems ACo/d-Frege+∀red by formulas of depth independent of d. In the propositional case, all these results correspond to major open problems

Modeling and Simulation Methodologies for Digital Twin in Industry 4.0

The concept of Industry 4.0 represents an innovative vision of what will be the factory of the future. The principles of this new paradigm are based on interoperability and data exchange between dierent industrial equipment. In this context, Cyber- Physical Systems (CPSs) cover one of the main roles in this revolution. The combination of models and the integration of real data coming from the field allows to obtain the virtual copy of the real plant, also called Digital Twin. The entire factory can be seen as a set of CPSs and the resulting system is also called Cyber-Physical Production System (CPPS). This CPPS represents the Digital Twin of the factory with which it would be possible analyze the real factory. The interoperability between the real industrial equipment and the Digital Twin allows to make predictions concerning the quality of the products. More in details, these analyses are related to the variability of production quality, prediction of the maintenance cycle, the accurate estimation of energy consumption and other extra-functional properties of the system. Several tools [2] allow to model a production line, considering dierent aspects of the factory (i.e. geometrical properties, the information flows etc.) However, these simulators do not provide natively any solution for the design integration of CPSs, making impossible to have precise analysis concerning the real factory. Furthermore, for the best of our knowledge, there are no solution regarding a clear integration of data coming from real equipment into CPS models that composes the entire production line. In this context, the goal of this thesis aims to define an unified methodology to design and simulate the Digital Twin of a plant, integrating data coming from real equipment. In detail, the presented methodologies focus mainly on: integration of heterogeneous models in production line simulators; Integration of heterogeneous models with ad-hoc simulation strategies; Multi-level simulation approach of CPS and integration of real data coming from sensors into models. All the presented contributions produce an environment that allows to perform simulation of the plant based not only on synthetic data, but also on real data coming from equipments

Securing mobile agent in hostile environment.

by Mo Chun Man.Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.Includes bibliographical references (leaves 72-80).Abstracts in English and Chinese.Chapter 1 --- INTRODUCTION --- p.1Chapter 1.1 --- The Mobile Agents --- p.2Chapter 1.2 --- The Mobile Agent Paradigm --- p.4Chapter 1.2.1 --- Initiatives --- p.5Chapter 1.2.2 --- Applications --- p.7Chapter 1.3 --- The Mobile Agent S ystem --- p.8Chapter 1.4 --- Security in Mobile Agent System --- p.9Chapter 1.5 --- Thesis Organization --- p.11Chapter 2 --- BACKGROUND AND FOUNDATIONS --- p.12Chapter 2.1 --- Encryption/Decryption --- p.12Chapter 2.2 --- One-way Hash Function --- p.13Chapter 2.3 --- Message Authentication Code (MAC) --- p.13Chapter 2.4 --- Homomorphic Encryption Scheme --- p.14Chapter 2.5 --- One-Round Oblivious Transfer --- p.14Chapter 2.6 --- Polynomial-time Algorithms --- p.14Chapter 2.7 --- Circuit --- p.15Chapter 3 --- SURVEY OF PROTECTION SCHEMES ON MOBILE AGENTS --- p.16Chapter 3.1 --- Introduction --- p.16Chapter 3.2 --- Detection Approaches --- p.17Chapter 3.2.1 --- Execution Traces --- p.17Chapter 3.2.2 --- Partial Result Encapsulation --- p.18Chapter 3.2.3 --- State Appraisal --- p.20Chapter 3.3 --- Prevention Approaches --- p.20Chapter 3.3.1 --- Sliding Encryption --- p.20Chapter 3.3.2 --- Tamper-resistant Hardware --- p.21Chapter 3.3.3 --- Multi-agent Cooperation --- p.22Chapter 3.3.4 --- Code Obfuscation --- p.23Chapter 3.3.5 --- Intention Spreading and Shrinking --- p.26Chapter 3.3.6 --- Encrypted Function Evaluation --- p.26Chapter 3.3.7 --- Black Box Test Prevention --- p.27Chapter 3.4 --- Chapter Summary --- p.29Chapter 4 --- TAXONOMY OF ATTACKS --- p.30Chapter 4.1 --- Introduction --- p.30Chapter 4.2 --- Whatis attack? --- p.31Chapter 4.3 --- How can attacks be done? --- p.32Chapter 4.4 --- Taxonomy of Attacks --- p.33Chapter 4.4.1 --- Purposeful Attack --- p.33Chapter 4.4.2 --- Frivolous Attack --- p.36Chapter 4.4.3 --- The Full Taxonomy --- p.38Chapter 4.5 --- Using the Taxonomy --- p.38Chapter 4.5.1 --- Match to Existing Protection Schemes --- p.38Chapter 4.5.2 --- Insight to Potential Protection Schemes --- p.41Chapter 4.6 --- Chapter Summary --- p.42Chapter 5 --- PROTECTION FOR REACTIVE MOBILE AGENTS --- p.43Chapter 5.1 --- Introduction --- p.43Chapter 5.2 --- The Model --- p.45Chapter 5.2.1 --- The Non-reactive and Reactive Mobile Agent Model --- p.45Chapter 5.2.2 --- The Computation Flow --- p.47Chapter 5.2.3 --- An Example --- p.49Chapter 5.3 --- tools --- p.51Chapter 5.3.1 --- Encrypted Circuit Construction --- p.51Chapter 5.3.2 --- Circuit Cascading --- p.53Chapter 5.4 --- Proposed Protection Scheme --- p.54Chapter 5.4.1 --- Two-hop Protocol --- p.55Chapter 5.4.2 --- Multi-hop Protocol --- p.60Chapter 5.5 --- Security Analysis --- p.60Chapter 5.5.1 --- Security under Purposeful Attacks --- p.61Chapter 5.5.2 --- Security under Frivolous Attacks --- p.62Chapter 5.6 --- Improvements --- p.62Chapter 5.6.1 --- Basic Idea --- p.63Chapter 5.6.2 --- Input Retrieval Protocol --- p.63Chapter 5.6.3 --- Combating Frivolous Attacks --- p.65Chapter 5.7 --- Further Considerations --- p.66Chapter 5.8 --- Chapter Summary --- p.67Chapter 6 --- CONCLUSIONS --- p.68APPENDIX --- p.71BIBLIOGRAPHY --- p.7

Security First approach in development of Single-Page Application based on Angular

Recently a Single-Page Application (SPA) approach is getting attention even though this is based on JavaScript is not considered to be a safe programming language. In the SPA ecosystem developers often have to use many external dependencies. Detected vulnerabilities in these external dependencies are disclosed and updated in most cases by the community. Often, in-depth security analysis is not included during the development stage, due to project deadlines and other circumstances. It goes with number of complications. The most straightforward is to be vulnerable for cyber attacks which causes financial problems for companies. Currently law already includes penalties in case of data breaches. Moreover, detected vulnerable code delays projects due to necessary time to improve it. Sometimes it requires to change the whole architecture if the application was poorly designed or in case security was skipped completely in the early stage. It might lead even to putting changes in the architectural style once the application is already on the market. It does makes high pressure on software developers to fix it fast. The rush to deliver it as fast as possible can create new security risks, because in some scenarios it might take significant amount of time to change the design with security prioritization. Especially within the financial industry consequences of not including security during the design stage might be harmful. Companies in this industry are entrusted with high social trust and sensitive (personal) data. For such enterprises shortcomings in security might cause data, image and money loss. Cybercrime activities are intensifying and for some companies it might causes to be kicked out of business due to hacking. This important factor of software development is currently getting more attention. That is why providing security in an early stage of a project is important, as well should be considered as a prerequisite. Security should be integrally included in all parts of the development cycle: specification, design, implementation and testing. The desired result is a secure web application. Improving security might be done explicitly by using security analysis and enhance security accordingly to the results. However, implicit methods like clean code, programming best practices, proper architecture design also applies. Ideally, in a continuous security way. Programming best practices and countermeasures against web application security threats have been used to analyse and verify SPA security. In this research project, an Angular SPA has been developed with focus on security. It includes programming best practices, security analysis and number of different tests. The main goal was to develop a SPA based on the Angular framework with security first approach. An in-depth security analysis of the deployed application is then conducted with validation of these results