139,585 research outputs found
Secure bit commitment from relativistic constraints
We investigate two-party cryptographic protocols that are secure under
assumptions motivated by physics, namely relativistic assumptions
(no-signalling) and quantum mechanics. In particular, we discuss the security
of bit commitment in so-called split models, i.e. models in which at least some
of the parties are not allowed to communicate during certain phases of the
protocol. We find the minimal splits that are necessary to evade the
Mayers-Lo-Chau no-go argument and present protocols that achieve security in
these split models. Furthermore, we introduce the notion of local versus global
command, a subtle issue that arises when the split committer is required to
delegate non-communicating agents to open the commitment. We argue that
classical protocols are insecure under global command in the split model we
consider. On the other hand, we provide a rigorous security proof in the global
command model for Kent's quantum protocol [Kent 2011, Unconditionally Secure
Bit Commitment by Transmitting Measurement Outcomes]. The proof employs two
fundamental principles of modern physics, the no-signalling property of
relativity and the uncertainty principle of quantum mechanics.Comment: published version, IEEE format, 18 pages, 8 figure
A Formulation of the Potential for Communication Condition using C2KA
An integral part of safeguarding systems of communicating agents from covert
channel communication is having the ability to identify when a covert channel
may exist in a given system and which agents are more prone to covert channels
than others. In this paper, we propose a formulation of one of the necessary
conditions for the existence of covert channels: the potential for
communication condition. Then, we discuss when the potential for communication
is preserved after the modification of system agents in a potential
communication path. Our approach is based on the mathematical framework of
Communicating Concurrent Kleene Algebra (C2KA). While existing approaches only
consider the potential for communication via shared environments, the approach
proposed in this paper also considers the potential for communication via
external stimuli.Comment: In Proceedings GandALF 2014, arXiv:1408.556
Communicating Mobile Processes
This paper presents a new model for mobile processes in occam-pi. A process, embedded anywhere in a dynamically evolving network, may suspend itself mid-execution, be safely disconnected from its local environment, moved (by communication along a channel), reconnected to a new environment and reactivated. Upon reactivation, the process resumes execution from the same state (i.e. data values and code positions) it held when it suspended. Its view of its environment is unchanged, since that is abstracted by its synchronisation (e.g. channels and barriers) interface and that remains constant. The environment behind that interface will (usually) be completely different. The mobile process itself may contain any number of levels of dynamic sub-network. This model is simpler and, in some ways, more powerful than our earlier proposal, which required a process to terminate before it could be moved. Its formal semantics and implementation, however, throw up extra challenges. We present details and performance of an initial implementation
Relativistic quantum cryptography
In this thesis we explore the benefits of relativistic constraints for
cryptography. We first revisit non-communicating models and its applications in
the context of interactive proofs and cryptography. We propose bit commitment
protocols whose security hinges on communication constraints and investigate
its limitations. We explain how some non-communicating models can be justified
by special relativity and study the limitations of such models. In particular,
we present a framework for analysing security of multiround relativistic
protocols. The second part of the thesis is dedicated to analysing specific
protocols. We start by considering a recently proposed two-round quantum bit
commitment protocol. We propose a fault-tolerant variant of the protocol,
present a complete security analysis and report on an experimental
implementation performed in collaboration with an experimental group at the
University of Geneva. We also propose a new, multiround classical bit
commitment protocol and prove its security against classical adversaries. This
demonstrates that in the classical world an arbitrarily long commitment can be
achieved even if the agents are restricted to occupy a finite region of space.
Moreover, the protocol is easy to implement and we report on an experiment
performed in collaboration with the Geneva group.Comment: 123 pages, 9 figures, many protocols, a couple of theorems, certainly
not enough commas. PhD thesis supervised by Stephanie Wehner at Centre for
Quantum Technologies, Singapor
A Middleware for the Internet of Things
The Internet of Things (IoT) connects everyday objects including a vast array
of sensors, actuators, and smart devices, referred to as things to the
Internet, in an intelligent and pervasive fashion. This connectivity gives rise
to the possibility of using the tracking capabilities of things to impinge on
the location privacy of users. Most of the existing management and location
privacy protection solutions do not consider the low-cost and low-power
requirements of things, or, they do not account for the heterogeneity,
scalability, or autonomy of communications supported in the IoT. Moreover,
these traditional solutions do not consider the case where a user wishes to
control the granularity of the disclosed information based on the context of
their use (e.g. based on the time or the current location of the user). To fill
this gap, a middleware, referred to as the Internet of Things Management
Platform (IoT-MP) is proposed in this paper.Comment: 20 pages, International Journal of Computer Networks & Communications
(IJCNC) Vol.8, No.2, March 201
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