New efficient three-party quantum key distribution protocols

Most of the existing quantum key distribution protocols (QKDPs) assume that every communicating party is equipped with quantum devices (QDs), e.g., the qubit generating machine, or the quantum memory, or the qubit measuring machine. However, in the practical situation, these QDs are expensive, and a center may be the only party that affords to own these devices. Though Phoenix first realize the idea, their scheme only has 13 of qubit efficiency. This paper proposes two three-party QKDPs. The first QKDP with an honest center allows communicants to share a session key by only performing unitary operations. Moreover, considering the trustworthiness of the center, this paper further proposes the second QKDP without the assumption of a trusted center. Besides, the proposed three-party QKDPs provide better qubit efficiency than the other QKDPs due to the use of the quantum memory and the use of one-way hash function for the eavesdropping check, and the security of proposed QKDPs is shown in the sequence-of-games approach.