Fen-Zhuo Guo

Revisiting the security of quantum dialogue and bidirectional quantum secure direct communication

From the perspective of information theory and cryptography, the security of two quantum dialogue protocols and a bidirectional quantum secure direct communication (QSDC) protocol was analyzed, and it was pointed out that the transmitted information would be partly leaked out in them. That is, any eavesdropper can elicit some information about the secrets from the public annunciations of the legal users. This phenomenon should have been strictly forbidden in a quantum secure communication. In fact, this problem exists in quite a few recent proposals and, therefore, it deserves more research attention in the following related study.

Consistency of shared reference frames should be reexamined

In a recent Letter [G. Chiribella et al., Phys. Rev. Lett. 98, 120501 (2007)], four protocols were proposed to secretly transmit a reference frame. Here We point out that in these protocols an eavesdropper can change the transmitted reference frame without being detected, which means the consistency of the shared reference frames should be reexamined. The way to check the above consistency is discussed. It is shown that this problem is quite different from that in previous protocols of quantum cryptography.

CONTROLLED QUANTUM SECURE DIRECT COMMUNICATION WITH W STATE

Utilizing W state, which is much more robust than GHZ state, we propose a protocol for three-party controlled quantum secure direct communication (QSDC). The feature of this protocol is that the sender encodes the secret message directly on a sequence of particle states and faithfully transmits them to an arbitrary one of two receivers without revealing any information to a potential eavesdropper. On the other hand, we construct the efficient quantum circuit to implement the QSDC by means of primitive operations in quantum computation.

Quantum key distribution without alternative measurements and rotations

A quantum key distribution protocol based on entanglement swapping is proposed. Through choosing particles by twos from the sequence and performing Bell measurements, two communicators can detect eavesdropping and obtain the secure key. Because the two particles measured together are selected out randomly, we need neither alternative measurements nor rotations of the Bell states to obtain security.

Comment on 'Quantum secret sharing based on reusable Greenberger-Horne-Zeilinger states as secure carriers'

In a recent paper [S. Bagherinezhad and V. Karimipour, Phys. Rev. A 67, 044302 (2003)], a quantum secret sharing protocol based on reusable GHZ states was proposed. However, in this Comment, it is shown that this protocol is insecure if Eve employs a special strategy to attack.

On the information-splitting essence of two types of quantum key distribution protocols

Abstract With the help of a simple quantum key distribution (QKD) scheme, we discuss the relation between BB84-type protocols and two-step-type ones. It is shown that they have the same essence, that is, information splitting. The choice of an orthogonal carrier or a nonorthogonal carrier, which looks like the main difference between these two types of protocols, is not an important, even not a very explicit matter. This result is instructive for related scheme designing and security analyzing.

Comment on “Quantum key distribution for d -level systems with generalized Bell states”

In the paper published in Phys. Rev. A 65, 052331 (2002), an entanglement-based quantum key distribution protocol for

Discrete-time interacting quantum walks and quantum Hash schemes

d

Comment on 'Two-way protocols for quantum cryptography with a nonmaximally entangled qubit pair'

-level systems was proposed. However, in this Comment, it is shown that this protocol is insecure for a special attack strategy.

Practical quantum all-or-nothing oblivious transfer protocol

Through introducing discrete-time quantum walks on the infinite line and on circles, we present a kind of two-particle interacting quantum walk which has two kinds of interactions. We investigate the characteristics of this kind of quantum walk and the time evolution of the two particles. Then we put forward a kind of quantum Hash scheme based on two-particle interacting quantum walks and discuss their feasibility and security. The security of this kind of quantum Hash scheme relies on the infinite possibilities of the initial state rather than the algorithmic complexity of hard problems, which will greatly enhance the security of the Hash schemes.