LIPIcs

Fault-tolerant distributed algorithms play an important role in many critical/high-availability applications. These algorithms are notoriously difficult to implement correctly, due to asynchronous communication and the occurrence of faults, such as the network dropping messages or computers crashing. Nonetheless there is surprisingly little language and verification support to build distributed systems based on fault-tolerant algorithms. In this paper, we present some of the challenges that a designer has to overcome to implement a fault-tolerant distributed system. Then we review different models that have been proposed to reason about distributed algorithms and sketch how such a model can form the basis for a domain-specific programming language. Adopting a high-level programming model can simplify the programmer's life and make the code amenable to automated verification, while still compiling to efficiently executable code. We conclude by summarizing the current status of an ongoing language design and implementation project that is based on this idea

Programmeerimiskeeled turvalise ühisarvutuse rakenduste arendamiseks

Turvaline ühisarvutus on tehnoloogia, mis lubab mitmel sõltumatul osapoolel oma andmeid koos töödelda neis olevaid saladusi avalikustamata. Kui andmed on esitatud krüpteeritud kujul, tähendab see, et neid ei dekrüpteerita arvutuse käigus kordagi. Turvalise ühisarvutuse teoreetilised konstruktsioonid on teada olnud juba alates kaheksakümnendatest, kuid esimesed praktilised teostused ja rakendused, mis päris andmeid töötlesid, ilmusid alles natuke enam kui kümme aastat tagasi. Nüüdseks on turvalist ühisarvutust kasutatud mitmes praktilises rakenduses ning sellest on kujunenud oluline andmekaitsetehnoloogia. Turvalise ühisarvutuse rakenduste arendamine on keerukas. Vahendid, mis aitavad kaasa arendusprotsessile, on veel väga uued, ning raamistikud on sageli liiga aeglased praktiliste rakenduste jaoks. Rakendusi on endiselt võimelised arendama ainult krüptograafiaeksperdid. Käesoleva töö eesmärk on teha turvalise ühisarvutuse raamistikke paremaks ning muuta ühisarvutusrakenduste arendamist kergemaks. Väidame, et valdkon- naspetsiifiliste programmeerimiskeelte kasutamine võimaldab turvalise ühisarvu- tuse rakenduste ja raamistike ehitamist, mis on samaaegselt lihtsasti kasutatavad, hea jõudlusega, hooldatavad, usaldusväärsed ja võimelised suuri andmemahtusid töötlema. Peamise tulemusena esitleme kahte uut programmeerimiskeelt, mis on mõeldud turvalise ühisarvutuse jaoks. SecreC 2 on mõeldud turvalise ühisarvutuse rakendus- te arendamise lihtsustamiseks ja aitab kaasa sellele, et rakendused oleks turvalised ja efektiivsed. Teine keel on loodud turvalise ühisarvutuse protokollide arenda- miseks ning selle eesmärk on turvalise ühisarvutuse raamistikke paremaks muuta. Protokollide keel teeb raamistikke kiiremaks ja usaldusväärsemaks ning lihtsustab protokollide arendamist ja haldamist. Kirjeldame mõlemad keeled nii formaalselt kui mitteformaalselt. Näitame, kuidas mitmed rakendused ja prototüübid saavad neist keeltest kasu.Secure multi-party computation is a technology that allows several independent parties to cooperatively process their private data without revealing any secrets. If private inputs are given in encrypted form then the results will also be encrypted, and at no stage during processing are values ever decrypted. As a theoretical concept, the technology has been around since the 1980s, but the first practical implementations arose a bit more than a decade ago. Since then, secure multi-party computation has been used in practical applications, and has been established as an important method of data protection. Developing applications that use secure multi-party computation is challenging. The tools that help with development are still very young and the frameworks are often too slow for practical applications. Currently only experts in cryptography are able to develop secure multi-party applications. In this thesis we look how to improve secure multy-party computation frame- works and make the applications easier to develop. We claim that domain-specific programming languages enable to build secure multi-party applications and frame- works that are at the same time usable, efficient, maintainable, trustworthy, and practically scalable. The contribution of this thesis is the introduction of two new programming languages for secure multi-party computation. The SecreC 2 language makes secure multi-party computation application development easier, ensuring that the applications are secure and enabling them to be efficient. The second language is for developing low-level secure computation protocols. This language was created for improving secure multi-party computation frameworks. It makes the frameworks faster and more trustworthy, and protocols easier to develop and maintain. We give give both a formal and an informal overview of the two languages and see how they benefit multi-party applications and prototypes

Optimizing Secure Computation Programs with Private Conditionals

Secure multiparty computation platforms are often provided with a programming language that allows to write privacy-preserving applications without thinking of the underlying cryptography. The control flow of these programs is expensive to hide, hence they typically disallow branching on private values. The application programmers have to specify their programs in terms of allowed constructions, either using ad-hoc methods to avoid such branchings, or the general methodology of executing all branches and obliviously selecting the effects of one at the end. There may be compiler support for the latter. The execution of all branches introduces significant computational overhead. If the branches perform similar private operations, then it may make sense to compute repeating patterns only once, even though the necessary bookkeeping also has overheads. In this paper, we propose a program optimization doing exactly that, allowing the overhead of private conditionals to be reduced. The optimization is quite general, and can be applied to various privacy-preserving platforms

Programming Languages and Systems

This open access book constitutes the proceedings of the 29th European Symposium on Programming, ESOP 2020, which was planned to take place in Dublin, Ireland, in April 2020, as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2020. The actual ETAPS 2020 meeting was postponed due to the Corona pandemic. The papers deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Programming Languages and Systems

This open access book constitutes the proceedings of the 28th European Symposium on Programming, ESOP 2019, which took place in Prague, Czech Republic, in April 2019, held as Part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2019

Proceedings of the 21st Conference on Formal Methods in Computer-Aided Design – FMCAD 2021

The Conference on Formal Methods in Computer-Aided Design (FMCAD) is an annual conference on the theory and applications of formal methods in hardware and system verification. FMCAD provides a leading forum to researchers in academia and industry for presenting and discussing groundbreaking methods, technologies, theoretical results, and tools for reasoning formally about computing systems. FMCAD covers formal aspects of computer-aided system design including verification, specification, synthesis, and testing

Renforcement formel et automatique de politiques de sécurité dans des applications Android par réécriture

Autant les applications Android ont réussi à positionner Android parmi les systèmes d'exploitation les plus utilisés, autant elles ont facilité aux créateurs de maliciels de s'introduire et de compromettre ses appareils. Une longue liste de menaces causées par les applications téléchargées vise l'intégrité du système et la vie privée de ses utilisateurs. Malgré l'évolution incessante du système Android pour améliorer son mécanisme de sécurité, le niveau de sophistication des logiciels malveillants a augmenté et s'adapte continuellement avec les nouvelles mesures. L'une des principales faiblesses menaçant la sécurité de ce système est le manque abyssal d'outils et d'environnements permettant la spécification et la vérification formelle des comportements des applications avant que les dommages ne soient causés. À cet égard, les méthodes formelles semblent être le moyen le plus naturel et le plus sûr pour une spécification et une vérification rigoureuses et non ambiguës de telles applications. Notre objectif principal est de développer un cadre formel pour le renforcement de politiques de sécurité dans les applications Android. L'idée est d'établir une synergie entre le paradigme orienté aspect et les méthodes formelles. L'approche consiste à réécrire le programme de l'application en ajoutant des tests de sécurité à certains points soigneusement sélectionnés pour garantir le respect de la politique de sécurité. La version réécrite du programme préserve tous les bons comportements de la version originale qui sont conformes à la politique de sécurité et agit contre les mauvais.As much as they have positioned Android among the most widely used operating systems, Android applications have helped malware creators to break in and infect its devices. A long list of threats caused by downloaded applications targets the integrity of the system and the privacy of its users. While the Android system is constantly evolving to improve its security mechanism, the malware's sophistication level is skyrocketing and continuously adapting with the new measures. One of the main weaknesses threatening smartphone security is the abysmal lack of tools and environments that allow formal specification and verification of application behaviors before damage is done. In this regard, formal methods seem to be the most natural and secure way for rigorous and unambiguous specification and verification of such applications. Our ultimate goal is to formally enforce security policies on Android applications. The main idea is to establish a synergy between the aspect-oriented paradigm and formal methods such as the program rewriting technique. The approach consists of rewriting the application program by adding security tests at certain carefully selected points to ensure that the security policy is respected. The rewritten version of the program preserves all the good behaviors of the original one that comply with the security policy and acts against the bad ones

Preprocessing-Based Verification of Multiparty Protocols with Honest Majority

This paper presents a generic “GMW-style” method for turning passively secure protocols into protocols secure against covert attacks, adding relatively cheap offline preprocessing and post-execution verification phases. In the preprocessing phase, each party generates and shares a sufficient amount of verified multiplication triples that will be later used to assist that party’s proof. The execution phase, after which the computed result is already available to the parties, has only negligible overhead that comes from signatures on sent messages. In the postprocessing phase, the verifiers repeat the computation of the prover in secret-shared manner, checking that they obtain the same messages that the prover sent out during execution. The verification preserves the privacy guarantees of the original protocol. It is applicable to protocols doing computations over finite rings, even if the same protocol performs its computation over several distinct rings. We apply our verification method to the Sharemind platform for secure multiparty computations (SMC), evaluate its performance and compare it to other existing SMC platforms offering security against stronger than passive attackers

Tõhus peit- ja aktiivse ründaja vastu kaitstud turvaline ühisarvutus

Turvaline ühisarvutus on tänapäevase krüptograafia üks tähtsamaid kasutusviise, mis koondab elegantsed matemaatilised lahendused praktiliste rakenduste ehitamiseks, võimaldades mitmel erineval andmeomanikul sooritada oma andmetega suvalisi ühiseid arvutusi, ilma neid andmeid üksteisele avaldamata. Passiivse ründaja vastu turvalised protokollid eeldavad, et kõik osapooled käituvad ausalt. Aktiivse ründaja vastu turvalised protokollid ei lekita privaatseid andmeid sõltumata ründaja käitumisest. Käesolevas töös esitatakse üldine meetod, mis teisendab passiivse ründaja vastu turvalised ühisarvutusprotokollid turvaliseks aktiivse ründaja vastu. Meetod on optimeeritud kolme osapoolega arvutusteks üle algebraliste ringide; praktikas on see väga efektiivne mudel, mis teeb reaalse maailma rakendused teostatavateks. Meetod lisab esialgsele arvutusprotokollile täitmisjärgse verifitseerimisfaasi, mis muudab valesti käitunud osapooltel vahelejäämise vältimise tõenäosuse kaduvväikseks, säilitades esialgse protokolli turvagarantiid. Lisaks uurib käesolev töö rünnete uut eesmärki, mis seisneb mingi ausa osapoole vaate manipuleerimises sellisel viisil, et ta saaks midagi teada teise ausa osapoole privaatsete andmete kohta. Ründaja ise ei tarvitse seda infot üldse teada saada. Sellised ründed on olulised, sest need kohustavad ausat osapoolt tühjendama oma süsteemi teiste osapoolte andmetest, kuid see ülesanne võib olla päris mittetriviaalne. Eelnevalt pakutud verifitseerimismehhanisme täiendatakse nii, et privaatsed andmed oleksid kaitstud ka ausate osapoolte eest. Paljud ühisarvutusplatvormid on varustatud programmeerimiskeelega, mis võimaldab kirjutada privaatsust säilitavaid rakendusi ilma allolevale krüptograafiale mõtlemata. Juhul, kui programm sisaldab tingimuslauseid, kus arvutusharu valik sõltub privaatsetest andmetest, ei tohi ükski osapool haru valikust midagi teada, nii et üldjuhul peavad osapooled täitma kõik harud. Harude suure arvu kor-ral võib arvutuslik lisakulu olla ülisuur, sest enamik vahetulemustest visatakse ära. Käesolevas töös pakutakse selliseid lisakulusid vähendavat optimeerimist.Secure multiparty computation is one of the most important employments of modern cryptography, bringing together elegant mathematical solutions to build up useful practical applications. It allows several distinct data owners to perform arbitrary collaborative computation on their private data without leaking any information to each other. Passively secure protocols assume that all parties follow the protocol rules. Actively secure protocols do not leak private data regardless of the attacker’s behaviour. This thesis presents a generic method for turning passively secure multiparty protocols to actively secure ones. The method is optimized for three party computation over algebraic rings, which has proven to be quite an efficient model, making large real-world applications feasible. Our method adds to the protocol a post-execution verification phase that allows a misbehaving party to escape detection only with negligible probability. It preserves the privacy guarantees of the original protocol. In this thesis, we also study a new adversarial goal in multiparty protocols. The goal is to manipulate the view of some honest party in such a way, that this honest party learns the private data of some other honest party. The adversary itself might not learn this data at all. Such attacks are significant because they create a liability to the first honest party to clean its systems from the second honest party’s data, which may be a highly non-trivial task in practice. We check the security of our verification mechanism in this new model, and we propose some minor modifications that ensure data protection also from the honest parties. Many secure multiparty computation platforms come with a programming language that allows the developer to write privacy-preserving applications without thinking of the underlying cryptography. If a program contains conditional statements where the choice of the computational branch depends on private data, then no party should know which branch has been executed, so in general the parties need to execute all of them. If the number of branches is large, the computational overhead may be enormous, as most of the intermediate results are just discarded. In this thesis, we propose an automatic optimization that reduces this overhead