The Research Of Quantum Cryptography Protocols Based On Multi-particle Entangled States

Quantum cryptography is the synthesis of classical cryptography and quantum mechanics. Compared with classical cryptography, quantum cryptography can achieve theoretically unconditional security, because its security completely depends on the basic principles of quantum mechanics. Therefore, researchers have tried to use the basic principles of quantum mechanics to solve some secure problems that be solved impossibly and intractably by classical cryptography, such as digital signatures, key distribution, image watermark and so on. Based on these research results, a theoretical system has been formedAs one of most important quantum resources in the field of quantum information, quantum entangled states have a very significant properties, that is, entanglement. It has been utilized to design quite a few subtle quantum cryptography protocols, such as quantum key distribution, quantum teleportation, quantum parallel computing, and so on. In this paper, some common multi-particle entanglement state have been studied, and based on which four quantum cryptographic protocols have been proposed. These protocols are briefly described as follows.1. Fair quantum blind signature scheme based on Greenberger-Horne-Zeilinger states. In the scheme, we use a Hash function and random numbers to generate a bit sequence. According to that, signer, arbiter and sender can select three appropriate measurement bases, respectively. Then, each participant measures one particle of a GHZ state in his hands. Finally, the relevance of measurement results is used to generate a signature. Security analysis of the scheme indicates that the protocol satisfies the requirements of a fair blind signature scheme, i.e., non-forgeability, non-deniability, blindness and traceability.2. Multi-party quantum key distribution protocol with mutual authentication. The protocol utilizes the entangled properties of GHZ state to achieve multi-party quantum key distribution protocol with mutual authentication, and uses a one-way Hash function technology with key to authenticate the identity of each user. Security analysis shows that the protocol is secure in theory.3. A watermarking scheme for quantum image based on least significant bit. The scheme embedded a watermark image into some pixels of quantum carrier image by changing one bit of gray-scale value of carrier image, and the position of these pixels were decided by a private key. Only the copyright owner who possesses the private key can extract the watermark information under the condition of not knowing the original carrier image. The computer simulation results show the proposed watermark scheme realizes invisibility and flexibility.4. A robust watermark scheme for quantum image based on repetition code. the scheme firstly encodes the watermark image with repetition code, and then the encoded watermark information is embedded into some random pixels of quantum carrier image. The authorized person who only knows the embedded pixels and gray bit position can exactly extract the watermark. Moreover, due to using repetition code to process watermark image, the watermark scheme is capable of correcting inevitable errors to some extent. Besides, the scheme’s computer simulations results show that the proposed quantum watermark scheme is effective.