9,997 research outputs found
Artificial-Noise-Aided Physical Layer Phase Challenge-Response Authentication for Practical OFDM Transmission
Recently, we have developed a PHYsical layer Phase Challenge-Response
Authentication Scheme (PHY-PCRAS) for independent multicarrier transmission. In
this paper, we make a further step by proposing a novel artificial-noise-aided
PHY-PCRAS (ANA-PHY-PCRAS) for practical orthogonal frequency division
multiplexing (OFDM) transmission, where the Tikhonov-distributed artificial
noise is introduced to interfere with the phase-modulated key for resisting
potential key-recovery attacks whenever a static channel between two legitimate
users is unfortunately encountered. Then, we address various practical issues
for ANA-PHY-PCRAS with OFDM transmission, including correlation among
subchannels, imperfect carrier and timing recoveries. Among them, we show that
the effect of sampling offset is very significant and a search procedure in the
frequency domain should be incorporated for verification. With practical OFDM
transmission, the number of uncorrelated subchannels is often not sufficient.
Hence, we employ a time-separated approach for allocating enough subchannels
and a modified ANA-PHY-PCRAS is proposed to alleviate the discontinuity of
channel phase at far-separated time slots. Finally, the key equivocation is
derived for the worst case scenario. We conclude that the enhanced security of
ANA-PHY-PCRAS comes from the uncertainty of both the wireless channel and
introduced artificial noise, compared to the traditional challenge-response
authentication scheme implemented at the upper layer.Comment: 33 pages, 13 figures, submitted for possible publicatio
Block encryption of quantum messages
In modern cryptography, block encryption is a fundamental cryptographic
primitive. However, it is impossible for block encryption to achieve the same
security as one-time pad. Quantum mechanics has changed the modern
cryptography, and lots of researches have shown that quantum cryptography can
outperform the limitation of traditional cryptography.
This article proposes a new constructive mode for private quantum encryption,
named , which is a very simple method to construct quantum
encryption from classical primitive. Based on mode, we
construct a quantum block encryption (QBE) scheme from pseudorandom functions.
If the pseudorandom functions are standard secure, our scheme is
indistinguishable encryption under chosen plaintext attack. If the pseudorandom
functions are permutation on the key space, our scheme can achieve perfect
security. In our scheme, the key can be reused and the randomness cannot, so a
-bit key can be used in an exponential number of encryptions, where the
randomness will be refreshed in each time of encryption. Thus -bit key can
perfectly encrypt qubits, and the perfect secrecy would not be broken
if the -bit key is reused for only exponential times.
Comparing with quantum one-time pad (QOTP), our scheme can be the same secure
as QOTP, and the secret key can be reused (no matter whether the eavesdropping
exists or not). Thus, the limitation of perfectly secure encryption (Shannon's
theory) is broken in the quantum setting. Moreover, our scheme can be viewed as
a positive answer to the open problem in quantum cryptography "how to
unconditionally reuse or recycle the whole key of private-key quantum
encryption". In order to physically implement the QBE scheme, we only need to
implement two kinds of single-qubit gates (Pauli gate and Hadamard gate),
so it is within reach of current quantum technology.Comment: 13 pages, 1 figure. Prior version appears in
eprint.iacr.org(iacr/2017/1247). This version adds some analysis about
multiple-message encryption, and modifies lots of contents. There are no
changes about the fundamental result
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
Authentication of Quantum Messages
Authentication is a well-studied area of classical cryptography: a sender S
and a receiver R sharing a classical private key want to exchange a classical
message with the guarantee that the message has not been modified by any third
party with control of the communication line. In this paper we define and
investigate the authentication of messages composed of quantum states. Assuming
S and R have access to an insecure quantum channel and share a private,
classical random key, we provide a non-interactive scheme that enables S both
to encrypt and to authenticate (with unconditional security) an m qubit message
by encoding it into m+s qubits, where the failure probability decreases
exponentially in the security parameter s. The classical private key is 2m+O(s)
bits. To achieve this, we give a highly efficient protocol for testing the
purity of shared EPR pairs. We also show that any scheme to authenticate
quantum messages must also encrypt them. (In contrast, one can authenticate a
classical message while leaving it publicly readable.) This has two important
consequences: On one hand, it allows us to give a lower bound of 2m key bits
for authenticating m qubits, which makes our protocol asymptotically optimal.
On the other hand, we use it to show that digitally signing quantum states is
impossible, even with only computational security.Comment: 22 pages, LaTeX, uses amssymb, latexsym, time
Quantum non-malleability and authentication
In encryption, non-malleability is a highly desirable property: it ensures
that adversaries cannot manipulate the plaintext by acting on the ciphertext.
Ambainis, Bouda and Winter gave a definition of non-malleability for the
encryption of quantum data. In this work, we show that this definition is too
weak, as it allows adversaries to "inject" plaintexts of their choice into the
ciphertext. We give a new definition of quantum non-malleability which resolves
this problem. Our definition is expressed in terms of entropic quantities,
considers stronger adversaries, and does not assume secrecy. Rather, we prove
that quantum non-malleability implies secrecy; this is in stark contrast to the
classical setting, where the two properties are completely independent. For
unitary schemes, our notion of non-malleability is equivalent to encryption
with a two-design (and hence also to the definition of Ambainis et al.). Our
techniques also yield new results regarding the closely-related task of quantum
authentication. We show that "total authentication" (a notion recently proposed
by Garg, Yuen and Zhandry) can be satisfied with two-designs, a significant
improvement over the eight-design construction of Garg et al. We also show
that, under a mild adaptation of the rejection procedure, both total
authentication and our notion of non-malleability yield quantum authentication
as defined by Dupuis, Nielsen and Salvail.Comment: 20+13 pages, one figure. v2: published version plus extra material.
v3: references added and update
Small Pseudo-Random Families of Matrices: Derandomizing Approximate Quantum Encryption
A quantum encryption scheme (also called private quantum channel, or state
randomization protocol) is a one-time pad for quantum messages. If two parties
share a classical random string, one of them can transmit a quantum state to
the other so that an eavesdropper gets little or no information about the state
being transmitted. Perfect encryption schemes leak no information at all about
the message. Approximate encryption schemes leak a non-zero (though small)
amount of information but require a shorter shared random key. Approximate
schemes with short keys have been shown to have a number of applications in
quantum cryptography and information theory.
This paper provides the first deterministic, polynomial-time constructions of
quantum approximate encryption schemes with short keys. Previous constructions
(quant-ph/0307104) are probabilistic--that is, they show that if the operators
used for encryption are chosen at random, then with high probability the
resulting protocol will be a secure encryption scheme. Moreover, the resulting
protocol descriptions are exponentially long. Our protocols use keys of the
same length as (or better length than) the probabilistic constructions; to
encrypt qubits approximately, one needs bits of shared key.
An additional contribution of this paper is a connection between classical
combinatorial derandomization and constructions of pseudo-random matrix
families in a continuous space.Comment: 11 pages, no figures. In Proceedings of RANDOM 2004, Cambridge, MA,
August 200
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