Modeling Bitcoin Contracts by Timed Automata

Bitcoin is a peer-to-peer cryptographic currency system. Since its introduction in 2008, Bitcoin has gained noticeable popularity, mostly due to its following properties: (1) the transaction fees are very low, and (2) it is not controlled by any central authority, which in particular means that nobody can "print" the money to generate inflation. Moreover, the transaction syntax allows to create the so-called contracts, where a number of mutually-distrusting parties engage in a protocol to jointly perform some financial task, and the fairness of this process is guaranteed by the properties of Bitcoin. Although the Bitcoin contracts have several potential applications in the digital economy, so far they have not been widely used in real life. This is partly due to the fact that they are cumbersome to create and analyze, and hence risky to use. In this paper we propose to remedy this problem by using the methods originally developed for the computer-aided analysis for hardware and software systems, in particular those based on the timed automata. More concretely, we propose a framework for modeling the Bitcoin contracts using the timed automata in the UPPAAL model checker. Our method is general and can be used to model several contracts. As a proof-of-concept we use this framework to model some of the Bitcoin contracts from our recent previous work. We then automatically verify their security in UPPAAL, finding (and correcting) some subtle errors that were difficult to spot by the manual analysis. We hope that our work can draw the attention of the researchers working on formal modeling to the problem of the Bitcoin contract verification, and spark off more research on this topic

Assurance Cases in Model-Driven Development of the Pacemaker Software

We discuss the construction of an assurance case for the pace-maker software. The software is developed following a model-based technique that combined formal modeling of the system, systematic code generation from the formal model, and measurement of timing behavior of the implementation. We show how the structure of the assurance case reflects our development approach

Towards Assurance for Plug & Play Medical Systems

Traditional safety-critical systems are designed and integrated by a systems integrator. The system integrator can asses the safety of the completed system before it is deployed. In medicine, there is a desire to transition from the traditional approach to a new model wherein a user can combine various devices post-hoc to create a new composite system that addresses a specific clinical scenario. Ensuring the safety of these systems is challenging: Safety is a property of systems that arises from the interaction of system components and it’s not possible to asses overall system safety by assessing a single component in isolation. It is unlikely that end-users will have the engineering expertise or resources to perform safety assessments each time they create a new composite system. In this paper we describe a platform-oriented approach to providing assurance for plug & play medical systems as well as an associated assurance argument pattern

Quantum and random walks as universal generators of probability distributions

Quantum walks and random walks bear similarities and divergences. One of the most remarkable disparities affects the probability of finding the particle at a given location: typically, almost a flat function in the first case and a bell-shaped one in the second case. Here I show how one can impose any desired stochastic behavior (compatible with the continuity equation for the probability function) on both systems by the appropriate choice of time- and site-dependent coins. This implies, in particular, that one can devise quantum walks that show diffusive spreading without loosing coherence, as well as random walks that exhibit the characteristic fast propagation of a quantum particle driven by a Hadamard coin.Comment: 8 pages, 2 figures; revised and enlarged versio

Globalization as the “Pulping” of Landscapes: Forestry Capitalism’s North-South Territorial Accumulation

The article presents the findings of a long-term incorporated comparison of forestry capitalism's globalization process. Primary data was collected by participant observation in pulp investment areas in Brazil between 2004 and 2011 and semi-structured interviews with key industry personnel, particularly in Finland. It is argued that the key cyclic change in industrial forestry from innovation–capitalization to material–territorial accumulation explains why and how the industry has globalized to the south via industrial tree plantations. The interlinked northern (Finnish) and southern (Brazilian) cases reveal that industry trajectories are influenced by who controls the supply chains of commodities. The findings are relevant for theorizing about the globalization of natural resource exploitation sectors. Changes in agrarian political economies and agency of state, business, and social movement actors—that is, socio-ecological relations and landscapes—help to explain how and why national and global capitalism and its developmental–environmental impacts are transformed.Peer reviewe

Performance Analysis and Functional Verification of the Stop-and-Wait Protocol in HOL

Real-time systems usually involve a subtle interaction of a number of distributed components and have a high degree of parallelism, which makes their performance analysis quite complex. Thus, traditional techniques, such as simulation, or the state-based formal methods usually fail to produce reasonable results. In this paper, we propose to use higher-order-logic (HOL) theorem proving for the performance analysis of real-time systems. The idea is to formalize the real-time system as a logical conjunction of HOL predicates, whereas each one of these predicates define an autonomous component or process of the given real-time system. The random or unpredictable behavior found in these components is modeled as random variables. This formal specification can then be used in a HOL theorem prover to reason about both functional and performance related properties of the given real-time system. In order to illustrate the practical effectiveness of our approach, we present the analysis of the Stop-and-Wait protocol, which is a classical example of real-time systems. The functional correctness of the protocol is verified by proving that the protocol ensures reliable data transfers. Whereas, the average message delay relation is verified in HOL for the sake of performance analysis. The paper includes the protocol’s formalization details along with the HOL proof sketches for the major theorems

Religion without religion : The challenge of radical postmodern philosophy of religion

Religion without religion. The challenge of radical postmodern philosophy of religion. The aim of this study is to examine the central ideas of Mark C. Taylor, Don Cupitt, and Grace Jantzen on the subject of the philosophy of religion. The method is a qualitative, systematic analysis of the works of the aforementioned philosophers. The purpose is to present, analyze, identify, find connections, and to gain an understanding of the original texts. This thesis shows that radical postmodern religion is “religion without religion”. God is “dead” and the concept of God is seen as “writing”, an ideal, a relationship of meanings or a language. In ethics, there are no objective values or principles. People must create their own morality. Reality is each person´s concept of reality. Language is universal in that language and reality cannot be considered separately. The human subject is contingent and formed in the linguistic and social context. According to postmodern feminism, the ideas that men present as facts are often degrading to women, distort reality and support the power of men. For this reason, we should create a new kind of philosophy of religion and a new language that takes women into consideration. Finally, we will study some philosophers, who have used postmodern ideas in a more moderate manner. In this way, we will look for a balanced solution between modernism and postmodernism. This study shows that the postmodern idea of religion is very different from classical Christianity. Ethics becomes subjective, anarchistic and nihilistic. Epistemology is relativistic and the human being becomes the measure of all things. Objective reality becomes blurry. Language is seen to be game-like, and it has no relation to reality. The moral responsibility of a subject becomes problematic. Science and rationality come into question without the permanent core provided by our consciousness. Women are not in an epistemologically privileged position. The truth claims by either men or women must each be evaluated one at a time. Many postmodern ideas can successfully be made of use if used in moderate manner.Tämän tutkimuksen tarkoituksena on tarkastella Mark C. Taylorin, Don Cupittin ja Grace Jantzenin tärkeimpiä uskonnonfilosofisia ajatuksia. Metodina on käytetty kvalitatiivista, tutkijoiden teosten sisältöä tarkastelevaa systemaattista analyysia, jonka päämääränä on pyrkiä esittelemään, erittelemään, identifioimaan, luomaan yhteyksiä ja ymmärtämään lähdeaineistoa. Tutkimus osoittaa, että radikaali postmoderni uskonto on "uskontoa ilman uskontoa". Jumala on "kuollut", ja jumaluus käsitetään "kirjoitukseksi", ihanteeksi, merkityssuhteeksi tai kieleksi. Etiikassa ei ole objektiivisia arvoja tai periaatteita. Ihmisen on itse luotava itselleen oma moraalinsa. Todellisuus on meidän käsityksemme todellisuudesta. Kieli on universaalista siten, että kieltä ja todellisuutta ei voi erottaa toisistaan. Ihmissubjekti on kontingentti ja muodostuu kielellisessä ja sosiaalisessa kontekstissa. Postmodernin feminismin mukaan miesten esittämät totuusväitteet ovat usein naisia sortavia, todellisuutta vääristäviä ja miesten valtaa pönkittäviä. Sen vuoksi olisi luotava uutta naiset huomioonottavaa uskonnonfilosofiaa ja kieltä. Lopuksi tarkastellaan muutamia filosofeja, jotka ovat käyttäneet maltillisesti hyväkseen postmoderneja ideoita. Siten pyritään etsimään tasapainoista uskonnonfilosofista ratkaisua modernismin ja postmodernismin luomassa tilanteessa. Arviointi osoittaa, että radikaali postmoderni uskontokäsitys poikkeaa suuresti klassisesta kristinuskosta. Etiikka muodostuu subjektivistiseksi, anarkistiseksi ja nihilistiseksi. Epistemologia on relativistista, ja ihmisestä tulee kaiken mitta. Objektiivinen todellisuus tulee häilyväksi. Kieli käsitetään pelinluonteiseksi. Sillä ei ole kosketusta todellisuuteen. Subjektin moraalinen vastuu tulee ongelmalliseksi. Tiede ja rationaalisuus tulevat kyseenalaisiksi ilman tietoisuuden pysyvää keskusta. Sekä miesten että naisten esittämät tietoväitteet on arvioitava kukin tapaus erikseen. Monia postmoderneja ideoita voidaan käyttää onnistuneesti hyväksi maltillisella tavalla