Semiquantum-key distribution using less than four quantum states

Semi-quantum Key Distribution Protocol Based on Bell States

“…Lately, several semi-quantum key distribution protocols (SQKD) [11][12][13] were proposed. For example, Boyer, Kenigsberg and Mor [11] introduced the idea of semiquantum key distribution using four quantum states firstly, and for convenience we refer to the protocol as BKM2007.…”

“…The literature [11] put forward two QKD protocols with the constraint that one party only has the traditional ability, and proved the robustness of their protocols against attacks, namely, any attempt by the third party to obtain information will inevitably lead to some errors, which makes the legitimate users can discover the attack behavior. Subsequently Zou and Qiu et al, [13] has simplified the work of Boyer et al, namely, proposed a simplified version which only requires one quantum state, for convenience we refer to the protocol as ZQLWL2009. Zou et al, mainly proposed several different SQKD schemes in which one party can send three, two and one quantum states respectively, and the analysis showed these protocols are also completely robust.…”

“…So this kind of protocol is termed "QKD with traditional Bob" or "Semi-quantum key distribution (SQKD)", and whose running environment can be described as Figure 2. It is proved that the SQKD protocols [11][12][13] is completely robust, which is the key step in the security analysis of their protocol. We say a protocol is robust if any attempt by the third party to obtain the information of the INFO string (prior to Alice and Bob performing the error correction code operation) will inevitably lead to some errors, which makes the legitimate users can discover the attack behavior.…”

Quantum secret sharing with classical Bobs

“…The protocol in [8] is essentially a combination of two parallel BB84 key distribution protocols. Similarly, our protocol can be regarded as a combination of two parallel semi-quantum key distribution protocols [20]. However, the detailed security analysis presented in the next section is not trivial.…”

Passive switching scheme for two-way quantum key distribution setups

“…Recently, novel protocols that employ two-way quantum communication have been proposed: the qubits must make a full round trip between Alice and Bob, who act both as transmitters and as receivers. One class of such protocols, which is the main focus of this Letter, is called semi-quantum key distribution (SQKD), in which one of the parties is classical, whereas the other is quantum [2,3]. In this case, Alice prepares a qubit and then sends it to Bob, who can perform either one of the following operations: (i) do nothing, and reflect the qubit back to Alice in the same state (or in a different state obtained by a fixed unitary transformation); or (ii) measure the qubit in a fixed predetermined basis and resend a new one, corresponding to the measurement result, back to Alice.…”