The ping-pong protocol can be attacked without eavesdropping

Attack the ping-pong protocol without eavesdropping.Comment: PACS: 03.67.H

Multiparty Quantum Secret Sharing

Based on a quantum secure direct communication (QSDC) protocol [Phys. Rev. A69(04)052319], we propose a $(n,n)$-threshold scheme of multiparty quantum secret sharing of classical messages (QSSCM) using only single photons. We take advantage of this multiparty QSSCM scheme to establish a scheme of multiparty secret sharing of quantum information (SSQI), in which only all quantum information receivers collaborate can the original qubit be reconstructed. A general idea is also proposed for constructing multiparty SSQI schemes from any QSSCM scheme

Chosen-Plaintext Cryptanalysis of a Clipped-Neural-Network-Based Chaotic Cipher

In ISNN'04, a novel symmetric cipher was proposed, by combining a chaotic signal and a clipped neural network (CNN) for encryption. The present paper analyzes the security of this chaotic cipher against chosen-plaintext attacks, and points out that this cipher can be broken by a chosen-plaintext attack. Experimental analyses are given to support the feasibility of the proposed attack.Comment: LNCS style, 7 pages, 1 figure (6 sub-figures

Multiparty Quantum Secret Sharing Based on Entanglement Swapping

A multiparty quantum secret sharing (QSS) protocol is proposed by using swapping quantum entanglement of Bell states. The secret messages are imposed on Bell states by local unitary operations. The secret messages are split into several parts and each part is distributed to a party so that no action of a subset of all the parties but their entire cooperation is able to read out the secret messages. In addition, the dense coding is used in this protocol to achieve a high efficiency. The security of the present multiparty QSS against eavesdropping has been analyzed and confirmed even in a noisy quantum channel.Comment: 5 page

Breaking a chaos-noise-based secure communication scheme

This paper studies the security of a secure communication scheme based on two discrete-time intermittently-chaotic systems synchronized via a common random driving signal. Some security defects of the scheme are revealed: 1) the key space can be remarkably reduced; 2) the decryption is insensitive to the mismatch of the secret key; 3) the key-generation process is insecure against known/chosen-plaintext attacks. The first two defects mean that the scheme is not secure enough against brute-force attacks, and the third one means that an attacker can easily break the cryptosystem by approximately estimating the secret key once he has a chance to access a fragment of the generated keystream. Yet it remains to be clarified if intermittent chaos could be used for designing secure chaotic cryptosystems.Comment: RevTeX4, 11 pages, 15 figure

Single Qubit Quantum Secret Sharing

We present a simple and practical protocol for the solution of a secure multiparty communication task, the secret sharing, and its experimental realization. In this protocol, a secret message is split among several parties in a way that its reconstruction require the collaboration of the participating parties. In the proposed scheme the parties solve the problem by a sequential communication of a single qubit. Moreover we show that our scheme is equivalent to the use of a multiparty entangled GHZ state but easier to realize and better scalable in practical applications.Comment: 5 pages, 2 figures, submitted December 29, 200

Teleportation: from probability distributions to quantum states

The role of the off-diagonal density matrix elements of the entangled pair is investigated in quantum teleportation of a qbit. The dependence between them and the off-diagonal elements of the teleported density matrix is shown to be linear. In this way the ideal quantum teleportation is related to an entirely classical communication protocol: the one-time pad cypher. The latter can be regarded as the classical counterpart of Bennett's quantum teleportation scheme. The quantum-to-classical transition is demonstrated on the statistics of a gedankenexperiment.Comment: 11 pages, 1 figure, accepted for publication in J. Phys. A (Math. Gen.

Quantum secret sharing between multi-party and multi-party without entanglement

We propose a quantum secret sharing protocol between multi-party ($m$ members in group 1) and multi-party ($n$ members in group 2) using a sequence of single photons. These single photons are used directly to encode classical information in a quantum secret sharing process. In this protocol, all members in group 1 directly encode their respective keys on the states of single photons via unitary operations, then the last one (the $m^{th}$ member of group 1) sends $1/n$ of the resulting qubits to each of group 2. Thus the secret message shared by all members of group 1 is shared by all members of group 2 in such a way that no subset of each group is efficient to read the secret message, but the entire set (not only group 1 but also group 2) is. We also show that it is unconditionally secure. This protocol is feasible with present-day techniques.Comment: 6 pages, no figur

Quantum secret sharing with qudit graph states

We present a unified formalism for threshold quantum secret sharing using graph states of systems with prime dimension. We construct protocols for three varieties of secret sharing: with classical and quantum secrets shared between parties over both classical and quantum channels.Comment: 13 pages, 12 figures. v2: Corrected to reflect imperfections of (n,n) QQ protocol. Also changed notation from $(n,m)$ to $(k,n)$, corrected typos, updated references, shortened introduction. v3: Updated acknowledgement

On the difficult tradeoff between security and privacy: Challenges for the management of digital identities

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-19713-5_39The deployment of security measures can lead in many occasions to an infringement of users’ privacy. Indeed, nowadays we have many examples about surveillance programs or personal data breaches in online service providers. In order to avoid the latter problem, we need to establish security measures that do not involve a violation of privacy rights. In this communication we discuss the main challenges when conciliating information security and users’ privacy.This work was supported by Comunidad de Madrid (Spain) under the project S2013/ICE-3095-CM (CIBERDINE)