1,662 research outputs found
Fair and Robust Multi-party Computation Using a Global Transaction Ledger
Classical results on secure multi-party computation (MPC) imply that fully
secure computation, including fairness (either all parties get output or none)
and robustness (output delivery is guaranteed), is impossible unless a
majority of the parties is honest.
Recently, cryptocurrencies like Bitcoin where utilized to leverage the
fairness loss in MPC against a dishonest majority. The idea is that when the
protocol aborts in an unfair manner (i.e., after the adversary
receives output) then honest parties get compensated by
the adversarially controlled parties.
Our contribution is three-fold.
First, we put forth a new formal model of secure MPC with compensation and we show
how the introduction of suitable ledger and synchronization
functionalities makes it possible to express completely such protocols using standard
interactive Turing machines (ITM) circumventing the need for the use of extra features
that are outside the standard model as in previous works.
Second, our model, is expressed in the universal composition setting with global setup and is equipped
with a composition theorem that enables the design of protocols that compose safely
with each other and within larger environments where other protocols with compensation
take place; a composition theorem for MPC protocols with compensation was not known before.
Third, we introduce the first robust MPC protocol with compensation, i.e., an MPC protocol
where not only fairness is guaranteed (via compensation) but additionally the protocol is
guaranteed to deliver output to the parties that get engaged and therefore the adversary,
after an initial round of deposits, is not even able to mount a denial of service attack without having to suffer a monetary penalty.
Importantly, our robust MPC protocol requires only a {\em constant } number of
(coin-transfer and communication) rounds
SoK:Communication across distributed ledgers
Since the inception of Bitcoin, a plethora of distributed ledgers differing in design and purpose has been created. While by design, blockchains provide no means to securely communicate with external systems, numerous attempts towards trustless cross-chain communication have been proposed over the years. Today, cross-chain communication (CCC) plays a fundamental role in cryptocurrency exchanges, scalability efforts via sharding, extension of existing systems through sidechains, and bootstrapping of new blockchains. Unfortunately, existing proposals are designed ad-hoc for specific use-cases, making it hard to gain confidence in their correctness and composability. We provide the first systematic exposition of cross-chain communication protocols. We formalize the underlying research problem and show that CCC is impossible without a trusted third party, contrary to common beliefs in the blockchain community. With this result in mind, we develop a framework to design new and evaluate existing CCC protocols, focusing on the inherent trust assumptions thereof, and derive a classification covering the field of cross-chain communication to date. We conclude by discussing open challenges for CCC research and the implications of interoperability on the security and privacy of blockchains
On the Convergence of Blockchain and Internet of Things (IoT) Technologies
The Internet of Things (IoT) technology will soon become an integral part of
our daily lives to facilitate the control and monitoring of processes and
objects and revolutionize the ways that human interacts with the physical
world. For all features of IoT to become fully functional in practice, there
are several obstacles on the way to be surmounted and critical challenges to be
addressed. These include, but are not limited to cybersecurity, data privacy,
energy consumption, and scalability. The Blockchain decentralized nature and
its multi-faceted procedures offer a useful mechanism to tackle several of
these IoT challenges. However, applying the Blockchain protocols to IoT without
considering their tremendous computational loads, delays, and bandwidth
overhead can let to a new set of problems. This review evaluates some of the
main challenges we face in the integration of Blockchain and IoT technologies
and provides insights and high-level solutions that can potentially handle the
shortcomings and constraints of both IoT and Blockchain technologies.Comment: Includes 11 Pages, 3 Figures, To publish in Journal of Strategic
Innovation and Sustainability for issue JSIS 14(1
Centrally Banked Cryptocurrencies
Current cryptocurrencies, starting with Bitcoin, build a decentralized
blockchain-based transaction ledger, maintained through proofs-of-work that
also generate a monetary supply. Such decentralization has benefits, such as
independence from national political control, but also significant limitations
in terms of scalability and computational cost. We introduce RSCoin, a
cryptocurrency framework in which central banks maintain complete control over
the monetary supply, but rely on a distributed set of authorities, or
mintettes, to prevent double-spending. While monetary policy is centralized,
RSCoin still provides strong transparency and auditability guarantees. We
demonstrate, both theoretically and experimentally, the benefits of a modest
degree of centralization, such as the elimination of wasteful hashing and a
scalable system for avoiding double-spending attacks.Comment: 15 pages, 4 figures, 2 tables in Proceedings of NDSS 201
- …