The Research Of Quantum Cryptographic Protocols Based On Single-Particle States

Quantum cryptography is the synthesis of quantum mechanics and classical cryptography. Compared with most classical cryptographic systems whose security relies on the complexity of computation, quantum cryptography applies the funda-mental principles of quantum mechanics to ensure the unconditional security, thus attracts lots of worldwide researches. The development of quantum cryptography has been shifted from the original quantum key distribution towards the other im-portant branches of cryptography, such as quantum secure direct communication, arbitrated quantum signature, quantum private comparison, and so on.The quantum resource employed in quantum cryptographic protocols can be divided into two classes:entangled state and single-particle state. Because of the important non-locality of entangled state, entangle state is usually used to design some subtle quantum communications, such as quantum teleportation and quantum dense coding. However, under real conditions, it is very difficult to prepare, transmit and preserve any entangled state. In contrast, the single-particle state has no such flaws and should be considered prior quantum resource when designing quantum cryptographic protocols. This paper tries to show the significance of single-particle state in quantum cryptography by presenting and investigating three single-particle-state-based quantum cryptographic protocols. They are:1. Quantum secure direct communication with authentication using two nonorthog-onal single-particle states. In this protocol, a classical hash function is employed to achieve the function of authentication and two one-particle unitary operations are used to encode secret information. The security analysis shows that the pro-tocol is secure against some common attacks;2. Arbitrated quantum signature scheme based on reusable key. This scheme com-bines a classical hash function and random numbers to ensure the keys of signer and receivers reusable. The security analysis shows that the scheme can stand against some well-known forgery attacks and disavowal attacks;3. Quantum private comparison with d-level single-particle states. In the protocol, a semi-honest third party is introduced to help two participants compare the size relationship of their secrets without revealing them to any other people. It is shown that the protocol can resist both the inside attacks and outside attacks under the ideal conditions. Furthermore, the security in real circumstance is also discussed.