127,354 research outputs found
How to Work with Honest but Curious Judges? (Preliminary Report)
The three-judges protocol, recently advocated by Mclver and Morgan as an
example of stepwise refinement of security protocols, studies how to securely
compute the majority function to reach a final verdict without revealing each
individual judge's decision. We extend their protocol in two different ways for
an arbitrary number of 2n+1 judges. The first generalisation is inherently
centralised, in the sense that it requires a judge as a leader who collects
information from others, computes the majority function, and announces the
final result. A different approach can be obtained by slightly modifying the
well-known dining cryptographers protocol, however it reveals the number of
votes rather than the final verdict. We define a notion of conditional
anonymity in order to analyse these two solutions. Both of them have been
checked in the model checker MCMAS
On the Duality of Probing and Fault Attacks
In this work we investigate the problem of simultaneous privacy and integrity
protection in cryptographic circuits. We consider a white-box scenario with a
powerful, yet limited attacker. A concise metric for the level of probing and
fault security is introduced, which is directly related to the capabilities of
a realistic attacker. In order to investigate the interrelation of probing and
fault security we introduce a common mathematical framework based on the
formalism of information and coding theory. The framework unifies the known
linear masking schemes. We proof a central theorem about the properties of
linear codes which leads to optimal secret sharing schemes. These schemes
provide the lower bound for the number of masks needed to counteract an
attacker with a given strength. The new formalism reveals an intriguing duality
principle between the problems of probing and fault security, and provides a
unified view on privacy and integrity protection using error detecting codes.
Finally, we introduce a new class of linear tamper-resistant codes. These are
eligible to preserve security against an attacker mounting simultaneous probing
and fault attacks
Unifying type systems for mobile processes
We present a unifying framework for type systems for process calculi. The
core of the system provides an accurate correspondence between essentially
functional processes and linear logic proofs; fragments of this system
correspond to previously known connections between proofs and processes. We
show how the addition of extra logical axioms can widen the class of typeable
processes in exchange for the loss of some computational properties like
lock-freeness or termination, allowing us to see various well studied systems
(like i/o types, linearity, control) as instances of a general pattern. This
suggests unified methods for extending existing type systems with new features
while staying in a well structured environment and constitutes a step towards
the study of denotational semantics of processes using proof-theoretical
methods
Different Approaches to Proof Systems
The classical approach to proof complexity perceives proof systems as deterministic, uniform, surjective, polynomial-time computable functions that map strings to (propositional) tautologies. This approach has been intensively studied since the late 70’s and a lot of progress has been made. During the last years research was started investigating alternative notions of proof systems. There are interesting results stemming from dropping the uniformity requirement, allowing oracle access, using quantum computations, or employing probabilism. These lead to different notions of proof systems for which we survey recent results in this paper
Process Calculi Abstractions for Biology
Several approaches have been proposed to model biological systems by means of the formal techniques and tools available in computer science. To mention just a few of them, some representations are inspired by Petri Nets theory, and some other by stochastic processes. A most recent approach consists in interpreting the living entities as terms of process calculi where the behavior of the represented systems can be inferred by applying syntax-driven rules. A comprehensive picture of the state of the art of the process calculi approach to biological modeling is still missing. This paper goes in the direction of providing such a picture by presenting a comparative survey of the process calculi that have been used and proposed to describe the behavior of living entities. This is the preliminary version of a paper that was published in Algorithmic Bioprocesses. The original publication is available at http://www.springer.com/computer/foundations/book/978-3-540-88868-
Challenges in computational lower bounds
We draw two incomplete, biased maps of challenges in computational complexity
lower bounds
A universe of processes and some of its guises
Our starting point is a particular `canvas' aimed to `draw' theories of
physics, which has symmetric monoidal categories as its mathematical backbone.
In this paper we consider the conceptual foundations for this canvas, and how
these can then be converted into mathematical structure. With very little
structural effort (i.e. in very abstract terms) and in a very short time span
the categorical quantum mechanics (CQM) research program has reproduced a
surprisingly large fragment of quantum theory. It also provides new insights
both in quantum foundations and in quantum information, and has even resulted
in automated reasoning software called `quantomatic' which exploits the
deductive power of CQM. In this paper we complement the available material by
not requiring prior knowledge of category theory, and by pointing at
connections to previous and current developments in the foundations of physics.
This research program is also in close synergy with developments elsewhere, for
example in representation theory, quantum algebra, knot theory, topological
quantum field theory and several other areas.Comment: Invited chapter in: "Deep Beauty: Understanding the Quantum World
through Mathematical Innovation", H. Halvorson, ed., Cambridge University
Press, forthcoming. (as usual, many pictures
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