1,310 research outputs found
Using quantum key distribution for cryptographic purposes: a survey
The appealing feature of quantum key distribution (QKD), from a cryptographic
viewpoint, is the ability to prove the information-theoretic security (ITS) of
the established keys. As a key establishment primitive, QKD however does not
provide a standalone security service in its own: the secret keys established
by QKD are in general then used by a subsequent cryptographic applications for
which the requirements, the context of use and the security properties can
vary. It is therefore important, in the perspective of integrating QKD in
security infrastructures, to analyze how QKD can be combined with other
cryptographic primitives. The purpose of this survey article, which is mostly
centered on European research results, is to contribute to such an analysis. We
first review and compare the properties of the existing key establishment
techniques, QKD being one of them. We then study more specifically two generic
scenarios related to the practical use of QKD in cryptographic infrastructures:
1) using QKD as a key renewal technique for a symmetric cipher over a
point-to-point link; 2) using QKD in a network containing many users with the
objective of offering any-to-any key establishment service. We discuss the
constraints as well as the potential interest of using QKD in these contexts.
We finally give an overview of challenges relative to the development of QKD
technology that also constitute potential avenues for cryptographic research.Comment: Revised version of the SECOQC White Paper. Published in the special
issue on QKD of TCS, Theoretical Computer Science (2014), pp. 62-8
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
Symbolic Abstractions for Quantum Protocol Verification
Quantum protocols such as the BB84 Quantum Key Distribution protocol exchange
qubits to achieve information-theoretic security guarantees. Many variants
thereof were proposed, some of them being already deployed. Existing security
proofs in that field are mostly tedious, error-prone pen-and-paper proofs of
the core protocol only that rarely account for other crucial components such as
authentication. This calls for formal and automated verification techniques
that exhaustively explore all possible intruder behaviors and that scale well.
The symbolic approach offers rigorous, mathematical frameworks and automated
tools to analyze security protocols. Based on well-designed abstractions, it
has allowed for large-scale formal analyses of real-life protocols such as TLS
1.3 and mobile telephony protocols. Hence a natural question is: Can we use
this successful line of work to analyze quantum protocols? This paper proposes
a first positive answer and motivates further research on this unexplored path
A Quantum-Proof Non-Malleable Extractor, With Application to Privacy Amplification against Active Quantum Adversaries
In privacy amplification, two mutually trusted parties aim to amplify the
secrecy of an initial shared secret in order to establish a shared private
key by exchanging messages over an insecure communication channel. If the
channel is authenticated the task can be solved in a single round of
communication using a strong randomness extractor; choosing a quantum-proof
extractor allows one to establish security against quantum adversaries.
In the case that the channel is not authenticated, Dodis and Wichs (STOC'09)
showed that the problem can be solved in two rounds of communication using a
non-malleable extractor, a stronger pseudo-random construction than a strong
extractor.
We give the first construction of a non-malleable extractor that is secure
against quantum adversaries. The extractor is based on a construction by Li
(FOCS'12), and is able to extract from source of min-entropy rates larger than
. Combining this construction with a quantum-proof variant of the
reduction of Dodis and Wichs, shown by Cohen and Vidick (unpublished), we
obtain the first privacy amplification protocol secure against active quantum
adversaries
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
Non-Malleable Extractors and Codes, with their Many Tampered Extensions
Randomness extractors and error correcting codes are fundamental objects in
computer science. Recently, there have been several natural generalizations of
these objects, in the context and study of tamper resilient cryptography. These
are seeded non-malleable extractors, introduced in [DW09]; seedless
non-malleable extractors, introduced in [CG14b]; and non-malleable codes,
introduced in [DPW10].
However, explicit constructions of non-malleable extractors appear to be
hard, and the known constructions are far behind their non-tampered
counterparts.
In this paper we make progress towards solving the above problems. Our
contributions are as follows.
(1) We construct an explicit seeded non-malleable extractor for min-entropy
. This dramatically improves all previous results and gives a
simpler 2-round privacy amplification protocol with optimal entropy loss,
matching the best known result in [Li15b].
(2) We construct the first explicit non-malleable two-source extractor for
min-entropy , with output size and
error .
(3) We initiate the study of two natural generalizations of seedless
non-malleable extractors and non-malleable codes, where the sources or the
codeword may be tampered many times. We construct the first explicit
non-malleable two-source extractor with tampering degree up to
, which works for min-entropy , with
output size and error . We show that we can
efficiently sample uniformly from any pre-image. By the connection in [CG14b],
we also obtain the first explicit non-malleable codes with tampering degree
up to , relative rate , and error
.Comment: 50 pages; see paper for full abstrac
- âŠ