2,737 research outputs found
Safer in the Clouds (Extended Abstract)
We outline the design of a framework for modelling cloud computing
systems.The approach is based on a declarative programming model which takes
the form of a lambda-calculus enriched with suitable mechanisms to express and
enforce application-level security policies governing usages of resources
available in the clouds. We will focus on the server side of cloud systems, by
adopting a pro-active approach, where explicit security policies regulate
server's behaviour.Comment: In Proceedings ICE 2010, arXiv:1010.530
Data mining for detecting Bitcoin Ponzi schemes
Soon after its introduction in 2009, Bitcoin has been adopted by
cyber-criminals, which rely on its pseudonymity to implement virtually
untraceable scams. One of the typical scams that operate on Bitcoin are the
so-called Ponzi schemes. These are fraudulent investments which repay users
with the funds invested by new users that join the scheme, and implode when it
is no longer possible to find new investments. Despite being illegal in many
countries, Ponzi schemes are now proliferating on Bitcoin, and they keep
alluring new victims, who are plundered of millions of dollars. We apply data
mining techniques to detect Bitcoin addresses related to Ponzi schemes. Our
starting point is a dataset of features of real-world Ponzi schemes, that we
construct by analysing, on the Bitcoin blockchain, the transactions used to
perform the scams. We use this dataset to experiment with various machine
learning algorithms, and we assess their effectiveness through standard
validation protocols and performance metrics. The best of the classifiers we
have experimented can identify most of the Ponzi schemes in the dataset, with a
low number of false positives
Timed Session Types
Timed session types formalise timed communication protocols between two
participants at the endpoints of a session. They feature a decidable compliance
relation, which generalises to the timed setting the progress-based compliance
between untimed session types. We show a sound and complete technique to decide
when a timed session type admits a compliant one. Then, we show how to
construct the most precise session type compliant with a given one, according
to the subtyping preorder induced by compliance. Decidability of subtyping
follows from these results
A note on two notions of compliance
We establish a relation between two models of contracts: binary session
types, and a model based on event structures and game-theoretic notions. In
particular, we show that compliance in session types corresponds to the
existence of certain winning strategies in game-based contracts.Comment: In Proceedings ICE 2014, arXiv:1410.701
Dissecting Ponzi schemes on Ethereum: identification, analysis, and impact
Ponzi schemes are financial frauds which lure users under the promise of high
profits. Actually, users are repaid only with the investments of new users
joining the scheme: consequently, a Ponzi scheme implodes soon after users stop
joining it. Originated in the offline world 150 years ago, Ponzi schemes have
since then migrated to the digital world, approaching first the Web, and more
recently hanging over cryptocurrencies like Bitcoin. Smart contract platforms
like Ethereum have provided a new opportunity for scammers, who have now the
possibility of creating "trustworthy" frauds that still make users lose money,
but at least are guaranteed to execute "correctly". We present a comprehensive
survey of Ponzi schemes on Ethereum, analysing their behaviour and their impact
from various viewpoints
Honesty by typing
We propose a type system for a calculus of contracting processes. Processes may stipulate contracts, and then either behave honestly, by keeping the promises made, or not. Type safety guarantees that a typeable process is honest - that is, the process abides by the contract it has stipulated in all possible contexts, even those containing dishonest adversaries
Blockchain for social good: a quantitative analysis
The rise of blockchain technologies has given a boost to social good
projects, which are trying to exploit various characteristic features of
blockchains: the quick and inexpensive transfer of cryptocurrency, the
transparency of transactions, the ability to tokenize any kind of assets, and
the increase in trustworthiness due to decentralization. However, the swift
pace of innovation in blockchain technologies, and the hype that has surrounded
their "disruptive potential", make it difficult to understand whether these
technologies are applied correctly, and what one should expect when trying to
apply them to social good projects. This paper addresses these issues, by
systematically analysing a collection of 120 blockchain-enabled social good
projects. Focussing on measurable and objective aspects, we try to answer
various relevant questions: which features of blockchains are most commonly
used? Do projects have success in fund raising? Are they making appropriate
choices on the blockchain architecture? How many projects are released to the
public, and how many are eventually abandoned?Comment: In GOODTECHS 201
Choreographies in the wild
We investigate the use of choreographies in distributed scenarios where, as in the real world, mutually distrusting (and possibly dishonest) participants may be unfaithful to their expected behaviour. In our model, each participant advertises its promised behaviour as a contract. Participants may interact through multiparty sessions, created when their contracts allow to synthesise a choreography. We show that systems of honest participants (which always adhere to their contracts) enjoy progress and session fidelity
Oraculizando a los ciudadanos : Demagogia y profanación de las inscripciones oraculares en Caballeros de Aristófanes (vv. 818- 819)
Dentro de los ataques cómicos que el Morcillero emite a Paflagonio en Caballeros de Aristófanes, uno en particular describe las formas que le permitieron a este figurado Cleón construir su poder sobre Atenas. Luego de que el propio Paflagonio se comparara con el gran Temístocles, el Morcillero expone los modos perniciosos de hacer política: en vv. 818-819, dice que Paflagonio convirtió a Atenas en una ciudad pequeña "levantando muros a través de ella y oraculizando". La primera estrategia remite al dicho del "divide y triunfarás". La segunda, en cambio, hace referencia a una institución político-religiosa como la adivinación. El oráculo, que era un aparato ideológico de la polis ateniense, aparece en el drama como un mensaje legitimador de quien detenta o detentará el poder y Aristófanes echa un manto de sospecha sobre dicha institución sagrada que es manipulada con fines propagandísticos. Con base en estas reflexiones, esta ponencia se propone analizar en Caballeros la denuncia del Morcillero sobre el ocultamiento de los oráculos inscriptos, su vínculo con el contexto socio- histórico de su inscripción y los motivos cómicos que subyacen en la operatoria de profanación de los mensajes divinosWith the comic critics that the Sausage-seller does against Paphlagon in Knights, Aristophanes describes how the demagogue Cleon builds up his power over Athenas. After the comparison with Themistocles, the Sausage-seller explains two injurious ways of doing politics: in vv. 818- 819, he accuses Paplagon of destroyng the greatness of the Athenian's city "by rearing barriers between them and chanting oracles". The first acussation talks about the strategy of fomenting hostility between classes. The second one makes reference to a religious and politic institution like the divination. The oracle, that was a ideological apparatus of the athenian polis, is showed in the comedy as the legitimized message about who holds or will hold the power. Thus Aristophanes blames the manipulation of that sacred institution with propagandistic purposes. This paper aims to analyze the Sausage-seller's accusation against the hidden writing oracle, its socio-historical context of inscription and the comic representation that lies beneath the divine message's profanatio
Contract agreements via logic
We relate two contract models: one based on event structures and game theory,
and the other one based on logic. In particular, we show that the notions of
agreement and winning strategies in the game-theoretic model are related to
that of provability in the logical model.Comment: In Proceedings ICE 2013, arXiv:1310.401
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