66,829 research outputs found
Asymmetric Distributed Trust
Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust assumptions. They can be found at the core of many algorithms for implementing reliable broadcasts, shared memory, consensus and other problems. This paper introduces asymmetric Byzantine quorum systems that model subjective trust. Every process is free to choose which combinations of other processes it trusts and which ones it considers faulty. Asymmetric quorum systems strictly generalize standard Byzantine quorum systems, which have only one global trust assumption for all processes. This work also presents protocols that implement abstractions of shared memory and broadcast primitives with processes prone to Byzantine faults and asymmetric trust. The model and protocols pave the way for realizing more elaborate algorithms with asymmetric trust
Brief Announcement: Asymmetric Distributed Trust
Quorum systems are a key abstraction in distributed fault-tolerant computing for capturing trust assumptions. They can be found at the core of many algorithms for implementing reliable broadcasts, shared memory, consensus and other problems. This paper introduces asymmetric Byzantine quorum systems that model subjective trust. Every process is free to choose which combinations of other processes it trusts and which ones it considers faulty. Asymmetric quorum systems strictly generalize standard Byzantine quorum systems, which have only one global trust assumption for all processes. This work also presents protocols that implement abstractions of shared memory and broadcast primitives with processes prone to Byzantine faults and asymmetric trust. The model and protocols pave the way for realizing more elaborate algorithms with asymmetric trust
From Symmetric to Asymmetric Asynchronous Byzantine Consensus
Consensus is arguably one of the most important notions in distributed
computing. Among asynchronous, randomized, and signature-free implementations,
the protocols of Most\'efaoui et al. (PODC 2014 and JACM 2015) represent a
landmark result, which has been extended later and taken up in practical
systems. The protocols achieve optimal resilience and takes, in expectation,
only a constant expected number of rounds of quadratic message complexity.
Randomization is provided through a common-coin primitive. In traditional
consensus protocols, all involved processes adhere to a global, symmetric
failure model, typically only defined by bounds on the number of faulty
processes. Motivated by applications to blockchains, however, more flexible
trust assumptions have recently been considered. In particular, with asymmetric
trust, a process is free to choose which other processes it trusts and which
ones might collude against it. This paper revisits the optimal asynchronous
protocol of Most\'efaoui et al. and shows how to realize it with asymmetric
trust. The paper starts by pointing out in detail why some versions of this
protocol may violate liveness. Then it proposes a fix for the protocol that
does not affect its properties, but lets it regain the simplicity of its
original version (PODC 2014). At the same time, the paper shows how to realize
randomized signature-free asynchronous Byzantine consensus with asymmetric
quorums. This results in an optimal consensus protocol with subjective,
asymmetric trust and constant expected running time. It is suitable for
applications to blockchains, for instance
Efficient distributed tag-based encryption and its application to group signatures with efficient distributed traceability
In this work, we first formalize the notion of dynamic group signatures with distributed traceability, where the capability to trace signatures is distributed among n managers without requiring any interaction. This ensures that only the participation of all tracing managers permits tracing a signature, which reduces the trust placed in a single tracing manager. The threshold variant follows easily from our definitions and constructions. Our model offers strong security requirements. Our second contribution is a generic construction for the notion which has a concurrent join protocol, meets strong security requirements, and offers efficient traceability, i.e. without requiring tracing managers to produce expensive zero-knowledge proofs for tracing correctness. To dispense with the expensive zero-knowledge proofs required in the tracing, we deploy a distributed tag-based encryption with public verifiability. Finally, we provide some concrete instantiations, which, to the best of our knowledge, are the first efficient provably secure realizations in the standard model simultaneously offering all the aforementioned properties. To realize our constructions efficiently, we construct an efficient distributed (and threshold) tag-based encryption scheme that works in the efficient Type-III asymmetric bilinear groups. Our distributed tag-based encryption scheme yields short ciphertexts (only 1280 bits at 128-bit security), and is secure under an existing variant of the standard decisional linear assumption. Our tag-based encryption scheme is of independent interest and is useful for many applications beyond the scope of this paper. As a special case of our distributed tag-based encryption scheme, we get an efficient tag-based encryption scheme in Type-III asymmetric bilinear groups that is secure in the standard model
The Meeting of Acquaintances: A Cost-efficient Authentication Scheme for Light-weight Objects with Transient Trust Level and Plurality Approach
Wireless sensor networks consist of a large number of distributed sensor
nodes so that potential risks are becoming more and more unpredictable. The new
entrants pose the potential risks when they move into the secure zone. To build
a door wall that provides safe and secured for the system, many recent research
works applied the initial authentication process. However, the majority of the
previous articles only focused on the Central Authority (CA) since this leads
to an increase in the computation cost and energy consumption for the specific
cases on the Internet of Things (IoT). Hence, in this article, we will lessen
the importance of these third parties through proposing an enhanced
authentication mechanism that includes key management and evaluation based on
the past interactions to assist the objects joining a secured area without any
nearby CA. We refer to a mobility dataset from CRAWDAD collected at the
University Politehnica of Bucharest and rebuild into a new random dataset
larger than the old one. The new one is an input for a simulated authenticating
algorithm to observe the communication cost and resource usage of devices. Our
proposal helps the authenticating flexible, being strict with unknown devices
into the secured zone. The threshold of maximum friends can modify based on the
optimization of the symmetric-key algorithm to diminish communication costs
(our experimental results compare to previous schemes less than 2000 bits) and
raise flexibility in resource-constrained environments.Comment: 27 page
TCG based approach for secure management of virtualized platforms: state-of-the-art
There is a strong trend shift in the favor of adopting virtualization to get business benefits. The provisioning of virtualized enterprise resources is one kind of many possible scenarios. Where virtualization promises clear advantages it also poses new security challenges which need to be addressed to gain stakeholders confidence in the dynamics of new environment. One important facet of these challenges is establishing 'Trust' which is a basic primitive for any viable business model. The Trusted computing group (TCG) offers technologies and mechanisms required to establish this trust in the target platforms. Moreover, TCG technologies enable protecting of sensitive data in rest and transit. This report explores the applicability of relevant TCG concepts to virtualize enterprise resources securely for provisioning, establish trust in the target platforms and securely manage these virtualized Trusted Platforms
An Algebraic Model For Quorum Systems
Quorum systems are a key mathematical abstraction in distributed
fault-tolerant computing for capturing trust assumptions. A quorum system is a
collection of subsets of all processes, called quorums, with the property that
each pair of quorums have a non-empty intersection. They can be found at the
core of many reliable distributed systems, such as cloud computing platforms,
distributed storage systems and blockchains. In this paper we give a new
interpretation of quorum systems, starting with classical majority-based quorum
systems and extending this to Byzantine quorum systems. We propose an algebraic
representation of the theory underlying quorum systems making use of
multivariate polynomial ideals, incorporating properties of these systems, and
studying their algebraic varieties. To achieve this goal we will exploit
properties of Boolean Groebner bases. The nice nature of Boolean Groebner bases
allows us to avoid part of the combinatorial computations required to check
consistency and availability of quorum systems. Our results provide a novel
approach to test quorum systems properties from both algebraic and algorithmic
perspectives.Comment: 15 pages, 3 algorithm
Coevolution of trustful buyers and cooperative sellers in the trust game
Many online marketplaces enjoy great success. Buyers and sellers in
successful markets carry out cooperative transactions even if they do not know
each other in advance and a moral hazard exists. An indispensable component
that enables cooperation in such social dilemma situations is the reputation
system. Under the reputation system, a buyer can avoid transacting with a
seller with a bad reputation. A transaction in online marketplaces is better
modeled by the trust game than other social dilemma games, including the
donation game and the prisoner's dilemma. In addition, most individuals
participate mostly as buyers or sellers; each individual does not play the two
roles with equal probability. Although the reputation mechanism is known to be
able to remove the moral hazard in games with asymmetric roles, competition
between different strategies and population dynamics of such a game are not
sufficiently understood. On the other hand, existing models of reputation-based
cooperation, also known as indirect reciprocity, are based on the symmetric
donation game. We analyze the trust game with two fixed roles, where trustees
(i.e., sellers) but not investors (i.e., buyers) possess reputation scores. We
study the equilibria and the replicator dynamics of the game. We show that the
reputation mechanism enables cooperation between unacquainted buyers and
sellers under fairly generous conditions, even when such a cooperative
equilibrium coexists with an asocial equilibrium in which buyers do not buy and
sellers cheat. In addition, we show that not many buyers may care about the
seller's reputation under cooperative equilibrium. Buyers' trusting behavior
and sellers' reputation-driven cooperative behavior coevolve to alleviate the
social dilemma.Comment: 5 figure
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