1,607 research outputs found
Universally Composable Quantum Multi-Party Computation
The Universal Composability model (UC) by Canetti (FOCS 2001) allows for
secure composition of arbitrary protocols. We present a quantum version of the
UC model which enjoys the same compositionality guarantees. We prove that in
this model statistically secure oblivious transfer protocols can be constructed
from commitments. Furthermore, we show that every statistically classically UC
secure protocol is also statistically quantum UC secure. Such implications are
not known for other quantum security definitions. As a corollary, we get that
quantum UC secure protocols for general multi-party computation can be
constructed from commitments
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
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
Composable Security in the Bounded-Quantum-Storage Model
We present a simplified framework for proving sequential composability in the
quantum setting. In particular, we give a new, simulation-based, definition for
security in the bounded-quantum-storage model, and show that this definition
allows for sequential composition of protocols. Damgard et al. (FOCS '05,
CRYPTO '07) showed how to securely implement bit commitment and oblivious
transfer in the bounded-quantum-storage model, where the adversary is only
allowed to store a limited number of qubits. However, their security
definitions did only apply to the standalone setting, and it was not clear if
their protocols could be composed. Indeed, we first give a simple attack that
shows that these protocols are not composable without a small refinement of the
model. Finally, we prove the security of their randomized oblivious transfer
protocol in our refined model. Secure implementations of oblivious transfer and
bit commitment then follow easily by a (classical) reduction to randomized
oblivious transfer.Comment: 21 page
Quantum Cryptography Beyond Quantum Key Distribution
Quantum cryptography is the art and science of exploiting quantum mechanical
effects in order to perform cryptographic tasks. While the most well-known
example of this discipline is quantum key distribution (QKD), there exist many
other applications such as quantum money, randomness generation, secure two-
and multi-party computation and delegated quantum computation. Quantum
cryptography also studies the limitations and challenges resulting from quantum
adversaries---including the impossibility of quantum bit commitment, the
difficulty of quantum rewinding and the definition of quantum security models
for classical primitives. In this review article, aimed primarily at
cryptographers unfamiliar with the quantum world, we survey the area of
theoretical quantum cryptography, with an emphasis on the constructions and
limitations beyond the realm of QKD.Comment: 45 pages, over 245 reference
Universally composable and customizable post-processing for practical quantum key distribution
In quantum key distribution (QKD), a secret key is generated between two distant parties by transmitting quantum states. Experimental measurements on the quantum states are then transformed to a secret key by classical post-processing. Here, we propose a construction framework in which QKD classical post-processing can be custom made. Though seemingly obvious, the concept of concatenating classical blocks to form a whole procedure does not automatically apply to the formation of a quantum cryptographic procedure since the security of the entire QKD procedure rests on the laws of quantum mechanics and classical blocks are originally designed and characterized without regard to any properties of these laws. Nevertheless, we justify such concept of concatenating classical blocks in constructing QKD classical post-processing procedures, along with a relation to the universal-composability-security parameter. Consequently, effects arising from an actual QKD experiment, such as those due to the finiteness of the number of signals used, can be dealt with by employing suitable post-processing blocks. Lastly, we use our proposed customizable framework to build a comprehensive generic recipe for classical post-processing that one can follow to derive a secret key from the measurement outcomes in an actual experiment. © 2010 Elsevier Ltd. All rights reserved.postprin
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