Quantum key distribution by comparing Bell states

Quantum Key Distribution Using a χ-Type State

“…Here, it is worth stressing that they don't make χ -type state measurements until Alice and Bob ascertain that there is no eavesdropping in their quantum channel, in other words, after they finishes the security check, the eavesdropping isn't detected. We confess that the present QKD protocol is similar to that in the paper [17], and the difference between the two protocols is only that the present protocol uses χ -type states and Bell states are employed in the paper [17]. In addition, we still confess that the present QKD protocol has not the symmetry trait, that is, Alice's and Bob's roles in it are not equal.…”

Individual Attack on the Improved Multiparty Quantum Secret Sharing Protocol

“…So we may think that our individual attack should be the strongest attack on Lin et al improved multiparty QSS protocol. In the end, it is worth stressing that our individual attack is proposed by employing the Bell state comparison law [31]. This law has been recently applied in the designing of several attack strategies [28][29][30].…”

“…By comparing φ + 1h with ψ − 12 , Bob will get the operator σ y . This kind of Bell state comparison method and its comparison steps can be consulted in the paper [31]. When Alice requires Bob to announce his initial Bell state in the control mode, he may not directly say that it is ψ − ht , but tell the lie that it is σ y ψ − ht = φ + ht (here, σ y is the operator that Bob just compares Bell state to get).…”

Eavesdropping on the improved three-party quantum secret sharing protocol

“…Obviously, the trait of this attack is that the Bell state comparison and the entanglement swapping are employed. By the way, the Bell state comparison [26] has been also used in the proposed attack strategy [25]. In addition, after giving this attack, we further modify Lin et al .…”

“…Suppose that Bob's Bell state measurement outcome on photons a and h is ψ [26]. By the way, here the four operations I, σ x , σ y , σ z are similar to the four operators U 1 , U 2 , U 3 , U 4 in the paper [26].…”