23,741 research outputs found
Proof-of-Prestige: A Useful Work Reward System for Unverifiable Tasks
As cryptographic tokens and altcoins are increasingly being built to serve as
utility tokens, the notion of useful work consensus protocols, as opposed to
number-crunching PoW consensus, is becoming ever more important. In such
contexts, users get rewards from the network after they have carried out some
specific task useful for the network. While in some cases the proof of some
utility or service can be proved, the majority of tasks are impossible to
verify. In order to deal with such cases, we design Proof-of-Prestige (PoP) - a
reward system that can run on top of Proof-of-Stake blockchains. PoP introduces
prestige which is a volatile resource and, in contrast to coins, regenerates
over time. Prestige can be gained by performing useful work, spent when
benefiting from services and directly translates to users minting power. PoP is
resistant against Sybil and Collude attacks and can be used to reward workers
for completing unverifiable tasks, while keeping the system free for the
end-users. We use two exemplar use-cases to showcase the usefulness of PoP and
we build a simulator to assess the cryptoeconomic behaviour of the system in
terms of prestige transfer between nodes.Comment: 2019 IEEE International Conference on Blockchain and Cryptocurrency
(ICBC 2019
Privacy-Preserving Trust Management Mechanisms from Private Matching Schemes
Cryptographic primitives are essential for constructing privacy-preserving
communication mechanisms. There are situations in which two parties that do not
know each other need to exchange sensitive information on the Internet. Trust
management mechanisms make use of digital credentials and certificates in order
to establish trust among these strangers. We address the problem of choosing
which credentials are exchanged. During this process, each party should learn
no information about the preferences of the other party other than strictly
required for trust establishment. We present a method to reach an agreement on
the credentials to be exchanged that preserves the privacy of the parties. Our
method is based on secure two-party computation protocols for set intersection.
Namely, it is constructed from private matching schemes.Comment: The material in this paper will be presented in part at the 8th DPM
International Workshop on Data Privacy Management (DPM 2013
Design and implementation of extensible middleware for non-repudiable interactions
PhD ThesisNon-repudiation is an aspect of security that is concerned with the creation of irrefutable audits of
an interaction. Ensuring the audit is irrefutable and verifiable by a third party is not a trivial task.
A lot of supporting infrastructure is required which adds large expense to the interaction. This
infrastructure comprises, (i) a non-repudiation aware run-time environment, (ii) several purpose
built trusted services and (iii) an appropriate non-repudiation protocol. This thesis presents design
and implementation of such an infrastructure. The runtime environment makes use of several trusted
services to achieve external verification of the audit trail. Non-repudiation is achieved by executing
fair non-repudiation protocols. The Fairness property of the non-repudiation protocol allows a
participant to protect their own interests by preventing any party from gaining an advantage by
misbehaviour. The infrastructure has two novel aspects; extensibility and support for automated
implementation of protocols.
Extensibility is achieved by implementing the infrastructure in middleware and by presenting a
large variety of non-repudiable business interaction patterns to the application (a non-repudiable
interaction pattern is a higher level protocol composed from one or more non-repudiation protocols).
The middleware is highly configurable allowing new non-repudiation protocols and interaction
patterns to be easily added, without disrupting the application.
This thesis presents a rigorous mechanism for automated implementation of non-repudiation
protocols. This ensures that the protocol being executed is that which was intended and verified
by the protocol designer. A family of non-repudiation protocols are taken and inspected. This
inspection allows a set of generic finite state machines to be produced. These finite state machines
can be used to maintain protocol state and manage the sending and receiving of appropriate protocol
messages.
A concrete implementation of the run-time environment and the protocol generation techniques is
presented. This implementation is based on industry supported Web service standards and services.EPSRC, The Hewlett Packard Arjuna La
Simulatable security for quantum protocols
The notion of simulatable security (reactive simulatability, universal
composability) is a powerful tool for allowing the modular design of
cryptographic protocols (composition of protocols) and showing the security of
a given protocol embedded in a larger one. Recently, these methods have
received much attention in the quantum cryptographic community.
We give a short introduction to simulatable security in general and proceed
by sketching the many different definitional choices together with their
advantages and disadvantages.
Based on the reactive simulatability modelling of Backes, Pfitzmann and
Waidner we then develop a quantum security model. By following the BPW
modelling as closely as possible, we show that composable quantum security
definitions for quantum protocols can strongly profit from their classical
counterparts, since most of the definitional choices in the modelling are
independent of the underlying machine model.
In particular, we give a proof for the simple composition theorem in our
framework.Comment: Added proof of combination lemma; added comparison to the model of
Ben-Or, Mayers; minor correction
A P2P Optimistic Fair Exchange (OFE) Scheme For Personal Health Records Using Blockchain Technology
In today’s digital world, it is common to exchange sensitive data between different parties. There are many examples of sensitive data or documents that require a digital exchange, such as banking information, insurance data, health records. In many cases, the exchange exists between unknown and untrusted parties. Therefore, it is essential to execute the data exchange over a fair non-repudiation protocol. In digital communication, non-repudiation is undeniable evidence of one’s responsibility regarding the validity of any data he shares/receives. Usually, this is achieved by the use of a cryptographic digital signature. In this case, the parties cannot deny the authenticity of their digital signature. The protocol satisfies the fairness property if and only if it does not give the sender any advantages over the receiver or vice versa, at any step during the exchange process. Combining fair exchange and non-repudiation for digital exchange is critical in many applications and can be acquired with or without the involvement of any trusted third party (TTP). However, without the involvement of TTP, fairness becomes probabilistic, and the involvement of TTP can cause significant dependency on the third party. Therefore, a peer-to-peer (P2P) (aka offline) fair non-repudiation protocol that does not require a trusted third-party is desirable in many applications. Blockchain is designed in such a way that the network can handle the trustless environment and deliver the correct result. Thus, if the exchanges are done leveraging Blockchain, it will ensure true fairness, and at the same time, none of the participants have to deal with the trust issue. In this thesis we propose a P2P fair non-repudiation data exchange scheme by leveraging Blockchain and distributed ledger technology. The scheme combines on-chain and off-chain communication patterns to enable the exchange of personal health records between patients and healthcare providers. We provide an informal reasoning of the proposed scheme. Moreover, we propose a design and implementation agnostic to existing Blockchain platforms to enable unbiased evaluation of the proposed scheme. Finally, we make a comparative analysis of the result derived from our approach with the existing one
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