2,529 research outputs found
On the Cost of Modularity in Atomic Broadcast
Modularity is a desirable property of complex software systems, since it simplifies code reuse, verification, maintenance, etc. However, the use of loosely coupled modules introduces a performance overhead. This overhead is often considered negligible, but this is not always the case. This paper aims at casting some light on the cost, in terms of performance, that is incurred when designing a relevant group communication protocol with modularity in mind: atomic broadcast. We conduct our experiments using two versions of atomic broadcast: a modular version and a monolithic one. We then measure the performance of both implementations under different system loads. Our results show that the overhead introduced by modularity is strongly related to the level of stress to which the system is subjected, and in the worst cases, reaches approximately 50%
Discovering, quantifying, and displaying attacks
In the design of software and cyber-physical systems, security is often
perceived as a qualitative need, but can only be attained quantitatively.
Especially when distributed components are involved, it is hard to predict and
confront all possible attacks. A main challenge in the development of complex
systems is therefore to discover attacks, quantify them to comprehend their
likelihood, and communicate them to non-experts for facilitating the decision
process. To address this three-sided challenge we propose a protection analysis
over the Quality Calculus that (i) computes all the sets of data required by an
attacker to reach a given location in a system, (ii) determines the cheapest
set of such attacks for a given notion of cost, and (iii) derives an attack
tree that displays the attacks graphically. The protection analysis is first
developed in a qualitative setting, and then extended to quantitative settings
following an approach applicable to a great many contexts. The quantitative
formulation is implemented as an optimisation problem encoded into
Satisfiability Modulo Theories, allowing us to deal with complex cost
structures. The usefulness of the framework is demonstrated on a national-scale
authentication system, studied through a Java implementation of the framework.Comment: LMCS SPECIAL ISSUE FORTE 201
FairLedger: A Fair Blockchain Protocol for Financial Institutions
Financial institutions are currently looking into technologies for
permissioned blockchains. A major effort in this direction is Hyperledger, an
open source project hosted by the Linux Foundation and backed by a consortium
of over a hundred companies. A key component in permissioned blockchain
protocols is a byzantine fault tolerant (BFT) consensus engine that orders
transactions. However, currently available BFT solutions in Hyperledger (as
well as in the literature at large) are inadequate for financial settings; they
are not designed to ensure fairness or to tolerate selfish behavior that arises
when financial institutions strive to maximize their own profit.
We present FairLedger, a permissioned blockchain BFT protocol, which is fair,
designed to deal with rational behavior, and, no less important, easy to
understand and implement. The secret sauce of our protocol is a new
communication abstraction, called detectable all-to-all (DA2A), which allows us
to detect participants (byzantine or rational) that deviate from the protocol,
and punish them. We implement FairLedger in the Hyperledger open source
project, using Iroha framework, one of the biggest projects therein. To
evaluate FairLegder's performance, we also implement it in the PBFT framework
and compare the two protocols. Our results show that in failure-free scenarios
FairLedger achieves better throughput than both Iroha's implementation and PBFT
in wide-area settings
An Evaluation of the Amoeba Group Communication System
The Amoeba group communication system has two unique aspects: (1) it uses a sequencer-based protocol with negative acknowledgements for achieving a total order on all group messages; and (2) users choose the degree of fault tolerance they desire. This paper reports on our design decisions in retrospect, the performance of the Amoeba group system, and our experiences using the system. We conclude that sequencer-based group protocols achieve high performance (comparable to Amoeba's fast remote procedure call implementation), that the scalability of our sequencer-based protocols is limited by message processing time, and that the flexibility and modularity of user-level implementations of protocols is likely to outweigh the potential performance loss
A Methodology and Supporting Tools for the Development of Component-Based Embedded Systems.
International audienceThe paper presents a methodology and supporting tools for developing component-based embedded systems running on resource- limited hardware platforms. The methodology combines two complementary component frameworks in an integrated tool chain: BIP and Think. BIP is a framework for model-based development including a language for the description of heterogeneous systems, as well as associated simulation and verification tools. Think is a software component framework for the generation of small-footprint embedded systems. The tool chain allows generation, from system models described in BIP, of a set of func tionally equivalent Think components. From these and libraries including OS services for a given hardware platform, a minimal system can be generated. We illustrate the results by modeling and implementing a software MPEG encoder on an iPod
The Four Pillars of Crowdsourcing: A Reference Model
Crowdsourcing is an emerging business model where tasks are accomplished by the general public; the crowd. Crowdsourcing has been used in a variety of disciplines,
including information systems development, marketing and
operationalization. It has been shown to be a successful model in recommendation systems, multimedia design and evaluation, database design, and search engine evaluation. Despite the increasing academic and industrial interest in crowdsourcing,there is still a high degree of diversity in the interpretation and the application of the concept. This paper analyses the literature and deduces a taxonomy of crowdsourcing. The taxonomy is meant to represent the different configurations of crowdsourcing in its main four pillars: the crowdsourcer, the crowd, the crowdsourced task and the crowdsourcing platform. Our outcome will help researchers and developers as a reference model to concretely and precisely state their particular interpretation and configuration of crowdsourcing
Towards a Unified Quantum Protocol Framework: Classification, Implementation, and Use Cases
We present a framework for the unification and standardization of quantum
network protocols, making their realization easier and expanding their use
cases to a broader range of communities interested in quantum technologies. Our
framework is available as an open-source repository, the Quantum Protocol Zoo.
We follow a modular approach by identifying two key components: Functionality,
which connects real-world applications; and Protocol, which is a set of
instructions between two or many parties, at least one of which has a quantum
device. Based on the different stages of the quantum internet and use-case in
the commercialization of quantum communication, our framework classifies
quantum cryptographic functionalities and the various protocol designs
implementing these functionalities. Towards this classification, we introduce a
novel concept of resource visualization for quantum protocols, which includes
two interfaces: one to identify the building blocks for implementing a given
protocol and another to identify accessible protocols when certain physical
resources or functionalities are available. Such classification provides a
hierarchy of quantum protocols based on their use-case and resource allocation.
We have identified various valuable tools to improve its representation with a
range of techniques, from abstract cryptography to graphical visualizations of
the resource hierarchy in quantum networks. We elucidate the structure of the
zoo and its primary features in this article to a broader class of quantum
information scientists, physicists, computer science theorists and end-users.
Since its introduction in 2018, the quantum protocol zoo has been a cornerstone
in serving the quantum networks community in its ability to establish the use
cases of emerging quantum internet networks. In that spirit we also provide
some of the applications of our framework from different perspectives.Comment: 12 pages, 6 figure
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