2,761 research outputs found
Enhanced No-Go Theorem for Quantum Position Verification
Based on the instantaneous nonlocal quantum computation (INQC), Buhrman et
al. proposed an excellent attack strategy to quantum position verification
(QPV) protocols in 2011, and showed that, if the colluding adversaries are
allowed to previously share unlimited entangled states, it is impossible to
design an unconditionally secure QPV protocol in the previous model. Here,
trying to overcome this no-go theorem, we find some assumptions in the INQC
attack, which are implicit but essential for the success of this attack, and
present three different QPV protocols where these assumptions are not
satisfied. We show that for the general adversaries, who execute the attack
operations at every common time slot or the time when they detect the arrival
of the challenge signals from the verifiers, secure QPV is achievable. This
implies practically secure QPV can be obtained even if the adversaries is
allowed to share unlimited entanglement previously. Here by "practically" we
mean that in a successful attack the adversaries need launch a new round of
attack on the coming qubits with extremely high frequency so that none of the
possible qubits, which may be sent at random time, will be missed. On the other
side, using such Superdense INQC (SINQC) attack, the adversaries can still
attack the proposed protocols successfully in theory. The particular attack
strategies to our protocols are presented respectively. On this basis, we
demonstrate the impossibility of secure QPV with looser assumptions, i.e. the
enhanced no-go theorem for QPV.Comment: 19 pages, single column, 3 tables, 6 figure
Cryptanalysis of a multi-party quantum key agreement protocol with single particles
Recently, Sun et al. [Quant Inf Proc DOI: 10.1007/s11128-013-0569-x]
presented an efficient multi-party quantum key agreement (QKA) protocol by
employing single particles and unitary operations. The aim of this protocol is
to fairly and securely negotiate a secret session key among parties with a
high qubit efficiency. In addition, the authors claimed that no participant can
learn anything more than his/her prescribed output in this protocol, i.e., the
sub-secret keys of the participants can be kept secret during the protocol.
However, here we points out that the sub-secret of a participant in Sun et
al.'s protocol can be eavesdropped by the two participants next to him/her. In
addition, a certain number of dishonest participants can fully determine the
final shared key in this protocol. Finally, we discuss the factors that should
be considered when designing a really fair and secure QKA protocol.Comment: 7 page
Dense-Coding Attack on Three-Party Quantum Key Distribution Protocols
Cryptanalysis is an important branch in the study of cryptography, including
both the classical cryptography and the quantum one. In this paper we analyze
the security of two three-party quantum key distribution protocols (QKDPs)
proposed recently, and point out that they are susceptible to a simple and
effective attack, i.e. the dense-coding attack. It is shown that the
eavesdropper Eve can totally obtain the session key by sending entangled qubits
as the fake signal to Alice and performing collective measurements after
Alice's encoding. The attack process is just like a dense-coding communication
between Eve and Alice, where a special measurement basis is employed.
Furthermore, this attack does not introduce any errors to the transmitted
information and consequently will not be discovered by Alice and Bob. The
attack strategy is described in detail and a proof for its correctness is
given. At last, the root of this insecurity and a possible way to improve these
protocols are discussed.Comment: 6 pages, 3 figure
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