6,279 research outputs found
On the Power of Quantum Encryption Keys
The standard definition of quantum state randomization, which is the quantum
analog of the classical one-time pad, consists in applying some transformation
to the quantum message conditioned on a classical secret key . We
investigate encryption schemes in which this transformation is conditioned on a
quantum encryption key state instead of a classical string, and extend
this symmetric-key scheme to an asymmetric-key model in which copies of the
same encryption key may be held by several different people, but
maintaining information-theoretical security. We find bounds on the message
size and the number of copies of the encryption key which can be safely created
in these two models in terms of the entropy of the decryption key, and show
that the optimal bound can be asymptotically reached by a scheme using
classical encryption keys. This means that the use of quantum states as
encryption keys does not allow more of these to be created and shared, nor
encrypt larger messages, than if these keys are purely classical.Comment: 17 pages, 1 figur
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
Quantum cryptography: a practical information security perspective
Quantum Key Exchange (QKE, also known as Quantum Key Distribution or QKD)
allows communicating parties to securely establish cryptographic keys. It is a
well-established fact that all QKE protocols require that the parties have
access to an authentic channel. Without this authenticated link, QKE is
vulnerable to man-in-the-middle attacks. Overlooking this fact results in
exaggerated claims and/or false expectations about the potential impact of QKE.
In this paper we present a systematic comparison of QKE with traditional key
establishment protocols in realistic secure communication systems.Comment: 5 pages, new title, published version, minor changes onl
Field Test of Classical Symmetric Encryption with Continuous Variable Quantum Key Distribution
We report on the design and performance of a point-to-point classical
symmetric encryption link with fast key renewal provided by a Continuous
Variable Quantum Key Distribution (CVQKD) system. Our system was operational
and able to encrypt point-to-point communications during more than six months,
from the end of July 2010 until the beginning of February 2011. This field test
was the first demonstration of the reliability of a CVQKD system over a long
period of time in a server room environment. This strengthens the potential of
CVQKD for information technology security infrastructure deployments
Experimental Demonstration of Quantum Fully Homomorphic Encryption with Application in a Two-Party Secure Protocol
A fully homomorphic encryption system hides data from unauthorized parties while still allowing them to perform computations on the encrypted data. Aside from the straightforward benefit of allowing users to delegate computations to a more powerful server without revealing their inputs, a fully homomorphic cryptosystem can be used as a building block in the construction of a number of cryptographic functionalities. Designing such a scheme remained an open problem until 2009, decades after the idea was first conceived, and the past few years have seen the generalization of this functionality to the world of quantum machines. Quantum schemes prior to the one implemented here were able to replicate some features in particular use cases often associated with homomorphic encryption but lacked other crucial properties, for example, relying on continual interaction to perform a computation or leaking information about the encrypted data. We present the first experimental realization of a quantum fully homomorphic encryption scheme. To demonstrate the versatility of a a quantum fully homomorphic encryption scheme, we further present a toy two-party secure computation task enabled by our scheme
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