3 research outputs found
Electronic voting in the classical and quantum settings: modelling, design and analysis
This thesis explores the cryptographic field of electronic voting both in the
classical and quantum regime. In the classical setting, we look at the problem of
self-tallying elections, while in the quantum setting we initiate the formal study
of quantum voting according to the principles of modern cryptography.
The concept of a self-tallying election (STE) scheme was first introduced by
Kiayias and Yung [PKC 2002] and captures electronic voting schemes in which
the tallying authorities are the voters of the election themselves. This type of
electronic voting is particularly compatible with and suitable for (but not only)
Blockchain governance, where governance is expected to be maintained in a fully
distributed manner. In this thesis, we formalize the requirements for secure STE
schemes in the Universal Composability (UC) framework. Our model captures
the standard voting properties of eligibility, fairness, vote-privacy, and one voter-one vote. We present E-cclesia, a new family of STE schemes, and prove that
it securely UC realizes the STE functionality. We propose E-cclesia 1.0 , the
first concrete instantiation of E-cclesia using RSA accumulators in combination
with a novel time-lock encryption scheme, name Astrolabous, that surpasses
the limitations of previous ones. In addition, we provide a concrete security
definition of TLE schemes and we formally abstract the concept of TLE into an
ideal functionality following the real/ideal paradigm introduced by Canetti [IEEE
FOCS 2001]. On top of that, we show that a protocol that uses a pair of TLE
algorithms that satisfy these properties UC realises our ideal TLE functionality.
Finally, we provide a novel TLE construction and we show that it satisfies our
security definition making our whole argumentation of a fully-fledged E-cclesia
protocol sound.
All practical e-voting constructions rely on computational assumption to
satisfy various properties such as privacy and verifiability.
A milestone work published by Shor [IEEE SFCS 1994] indicates that well
known mathematical problems can be solved efficiently if we have at our disposal a
quantum computer. Recent advances indicate that quantum computers will soon
be a reality. Motivated by this ever more realistic threat for existing classical
cryptographic protocols, researchers have developed several schemes to resist
quantum attacks. In particular, several e-voting schemes relying on the properties
of quantum mechanics have been proposed for electronic voting. However, each of
these proposals comes with a different and often not well-articulated corruption model, has different objectives, and is accompanied by security claims that are
never formalized and justified only against specific attacks. To address this, we
propose the first formal security definitions for quantum e-voting protocols.
With these at hand, we systematize and evaluate the security of previously
proposed quantum e-voting protocols; we examine the claims of these works concerning privacy, correctness and verifiability, and if they are correctly attributed
to the proposed protocols. In all non-trivial cases, we identify specific quantum
attacks that violate these properties. We argue that the cause of these failures
lies in the absence of formal security models and references to the existing cryptographic literature
Head-Driven Phrase Structure Grammar
Head-Driven Phrase Structure Grammar (HPSG) is a constraint-based or declarative approach to linguistic knowledge, which analyses all descriptive levels (phonology, morphology, syntax, semantics, pragmatics) with feature value pairs, structure sharing, and relational constraints. In syntax it assumes that expressions have a single relatively simple constituent structure. This volume provides a state-of-the-art introduction to the framework. Various chapters discuss basic assumptions and formal foundations, describe the evolution of the framework, and go into the details of the main syntactic phenomena. Further chapters are devoted to non-syntactic levels of description. The book also considers related fields and research areas (gesture, sign languages, computational linguistics) and includes chapters comparing HPSG with other frameworks (Lexical Functional Grammar, Categorial Grammar, Construction Grammar, Dependency Grammar, and Minimalism)
Head-Driven Phrase Structure Grammar
Head-Driven Phrase Structure Grammar (HPSG) is a constraint-based or declarative approach to linguistic knowledge, which analyses all descriptive levels (phonology, morphology, syntax, semantics, pragmatics) with feature value pairs, structure sharing, and relational constraints. In syntax it assumes that expressions have a single relatively simple constituent structure. This volume provides a state-of-the-art introduction to the framework. Various chapters discuss basic assumptions and formal foundations, describe the evolution of the framework, and go into the details of the main syntactic phenomena. Further chapters are devoted to non-syntactic levels of description. The book also considers related fields and research areas (gesture, sign languages, computational linguistics) and includes chapters comparing HPSG with other frameworks (Lexical Functional Grammar, Categorial Grammar, Construction Grammar, Dependency Grammar, and Minimalism)