Security of the "ping-pong" quantum communication protocol recently proposed by Boström and Felbinger [Phys. Rev. Lett. 89, 187902 (2002)]] is analyzed in the case of considerable quantum channel losses. The eavesdropping scheme is presented, which reveals that the ping-pong protocol is not secure for transmission efficiencies lower than 60%. Our scheme induces 50% losses, which, however, can be hidden in the channel losses if one replaces the original lossy channel with a less lossy one. Finally, a possible improvement of the ping-pong protocol security is proposed.
We introduce an attack scheme for eavesdropping freely the ping-pong quantum communication protocol proposed by Boström and Felbinger [ Phys. Rev. Lett. 89 , 187902 (2002)] in a noise channel. The vicious eavesdropper, Eve, intercepts and measures the travel photon transmitted between the sender and the receiver. Then she replaces the quantum signal with a multi-photon signal in the same state, and measures the returned photons with the measuring basis, with which Eve prepares the fake signal except for one photon. This attack increases neither the quantum channel losses nor the error rate in the sampling instances for eavesdropping check. It works for eavesdropping the secret message transmitted with the ping-pong protocol. Finally, we propose a way for improving the security of the ping-pong protocol.
We show an eavesdropping scheme on Bostr\UNICODE{0xf6}m-Felbinger communication protocol (called ping-pong protocol) [Phys. Rev. Lett. 89, 187902 (2002)] in an ideal quantum channel. A measurement attack can be perfectly used to eavesdrop Alice's information instead of a most general quantum operation attack. In a noisy quantum channel, the direct communication is forbidden. We present a quantum key distribution protocol based on the ping-pong protocol, which can be used in a low noisy quantum channel. And we give a weak upper bound on the bit-error ratio that the detection probability
d should be lower than 0.11, which is a requirement criterion when we utilize the ping-pong protocol in a real communication.
Ping-Pong protocol is a Quantum Secure Direct Communication protocol that fails to transfer a secure key or secret message optimally in a lossy or noisy channel. The reason is an eavesdropper who possibly hides in the light of these channel losses and gains information about the secure key bits or secret messages. We propose an efficient modification to the control mode of the original Ping-Pong protocol leading to the detection of an eavesdropper with a much higher probability which may not allow her to hide in the light of lossy channels. Assuming that Eve knows and makes a fixed number of right guesses about the modification in the protocol, an optimum ratio of modification can be evaluated. In addition, it is shown that incorporation of the proposed modification in the protocol doubles the eavesdropper’s detection probability for certain eavesdropping operations.
A deterministic quantum communication protocol, called the ping-pong protocol, has been represented by Boström and Felbinger [Phys. Rev. Lett. 89 (2002) 187902]. Based on an entangled pair of photons, it allows asymptotically secure key distribution and quasi-secure direct communication. However, it was concluded from our previous research that the experiment realization of this protocol requires two optic paths strictly equivalent for interferometry. Here we propose an improved protocol, which is more flexible and secure for conceivable applications. Its feasibility and security are also discussed.
The eavesdropping scheme proposed by Wójcik [Phys. Rev. Lett. {\bf 90},157901(2003)] on the quantum communication protocol of Boström and Felbinger [Phys. Rev. Lett. {\bf 89}, 187902(2002)] is improved by constituting a new set of attack operations. The improved scheme only induces half of the eavesdropping losses in Wójcik's scheme, therefore, in a larger domain of the quantum channel transmission efficiency
η, i.e., [0,75%], the eavesdropper Eve can attack all the transmitted bits. Comparing to Wójcik's scheme, in the improved scheme the eavesdropping (legitimate) information gain does not vary in the
η domain of [0, 50%], while in the
η domain of (50%, 75%] the less eavesdropping losses induce more eavesdropping information gains, for Eve can attack {\it all} the transmitted bits and accordingly eavesdropping information gains do {\it not} decrease. Moreover, for the Boström-Felbinger protocol, the insecurity upper bound of
η presented by Wójcik is pushed up in the this paper, that is, according to Wójcik's eavesdropping scheme, the Boström-Felbinger protocol is not secure for transmission efficiencies lower than almost 60%, while according to the improved scheme, it is not secure for transmission efficiencies lower than almost 80%.
Ping-Pong quantum communication protocol may be employed to transmit deterministically information, so it has instrigued mang researchers. However, there are drawbacks on the security due to the symmetry of the employed two-way quantum channel. In this paper we propose a new attack strategy to eavesdrop the initially transmitted information based on the techniques of quantum error correction code (QECC). In addition, an attack strategy of Ping-Pong scheme based either entanglement state or nonorthogonal state is proofed and demonstrated, respectively. Furthermore, information obtained by Eve and the possible probability detected by the legitimate communicators are analyzed by employing information theorems. Detail proofs and analysis illustrate all previous Ping-Pong quantum communication schemes are insecure, i.e., the eavesdropper may obtain all available information without being detected.