5,411 research outputs found
On the Design of Cryptographic Primitives
The main objective of this work is twofold. On the one hand, it gives a brief
overview of the area of two-party cryptographic protocols. On the other hand,
it proposes new schemes and guidelines for improving the practice of robust
protocol design. In order to achieve such a double goal, a tour through the
descriptions of the two main cryptographic primitives is carried out. Within
this survey, some of the most representative algorithms based on the Theory of
Finite Fields are provided and new general schemes and specific algorithms
based on Graph Theory are proposed
Automated Cryptographic Analysis of the Pedersen Commitment Scheme
Aiming for strong security assurance, recently there has been an increasing
interest in formal verification of cryptographic constructions. This paper
presents a mechanised formal verification of the popular Pedersen commitment
protocol, proving its security properties of correctness, perfect hiding, and
computational binding. To formally verify the protocol, we extended the theory
of EasyCrypt, a framework which allows for reasoning in the computational
model, to support the discrete logarithm and an abstraction of commitment
protocols. Commitments are building blocks of many cryptographic constructions,
for example, verifiable secret sharing, zero-knowledge proofs, and e-voting.
Our work paves the way for the verification of those more complex
constructions.Comment: 12 pages, conference MMM-ACNS 201
Communication Complexity and Secure Function Evaluation
We suggest two new methodologies for the design of efficient secure
protocols, that differ with respect to their underlying computational models.
In one methodology we utilize the communication complexity tree (or branching
for f and transform it into a secure protocol. In other words, "any function f
that can be computed using communication complexity c can be can be computed
securely using communication complexity that is polynomial in c and a security
parameter". The second methodology uses the circuit computing f, enhanced with
look-up tables as its underlying computational model. It is possible to
simulate any RAM machine in this model with polylogarithmic blowup. Hence it is
possible to start with a computation of f on a RAM machine and transform it
into a secure protocol.
We show many applications of these new methodologies resulting in protocols
efficient either in communication or in computation. In particular, we
exemplify a protocol for the "millionaires problem", where two participants
want to compare their values but reveal no other information. Our protocol is
more efficient than previously known ones in either communication or
computation
Verifying Privacy-Type Properties in a Modular Way
Formal methods have proved their usefulness for analysing the security of protocols. In this setting, privacy-type security properties (e.g. vote-privacy, anonymity, unlink ability) that play an important role in many modern applications are formalised using a notion of equivalence. In this paper, we study the notion of trace equivalence and we show how to establish such an equivalence relation in a modular way. It is well-known that composition works well when the processes do not share secrets. However, there is no result allowing us to compose processes that rely on some shared secrets such as long term keys. We show that composition works even when the processes share secrets provided that they satisfy some reasonable conditions. Our composition result allows us to prove various equivalence-based properties in a modular way, and works in a quite general setting. In particular, we consider arbitrary cryptographic primitives and processes that use non-trivial else branches. As an example, we consider the ICAO e-passport standard, and we show how the privacy guarantees of the whole application can be derived from the privacy guarantees of its sub-protocols
Composability in quantum cryptography
In this article, we review several aspects of composability in the context of
quantum cryptography. The first part is devoted to key distribution. We discuss
the security criteria that a quantum key distribution protocol must fulfill to
allow its safe use within a larger security application (e.g., for secure
message transmission). To illustrate the practical use of composability, we
show how to generate a continuous key stream by sequentially composing rounds
of a quantum key distribution protocol. In a second part, we take a more
general point of view, which is necessary for the study of cryptographic
situations involving, for example, mutually distrustful parties. We explain the
universal composability framework and state the composition theorem which
guarantees that secure protocols can securely be composed to larger
applicationsComment: 18 pages, 2 figure
Provably correct Java implementations of Spi Calculus security protocols specifications
Spi Calculus is an untyped high level modeling language for security protocols, used for formal protocols specification and verification. In this paper, a type system for the Spi Calculus and a translation function are formally defined, in order to formalize the refinement of a Spi Calculus specification into a Java implementation. The Java implementation generated by the translation function uses a custom Java library. Formal conditions on such library are stated, so that, if the library implementation code satisfies such conditions, then the generated Java implementation correctly simulates the Spi Calculus specification. A verified implementation of part of the custom library is further presente
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