Quantum Key Distribution And Quantum Signature Theory Research

With the development of society, information exchange becomes more frequently than before. How to ensure the information security has become a hot topic of the present study. Quantum cryptography has two basic characters:uncondicational security and eavesdropping detectability, it provides new ways for transmitting message securely. This dissertation mainly involves two areas in quantum cryptography:quantum key distribution (QKD) and quantum signatures (QS).In the field of quantum key distribution, we analyze the progress of the six-state quantum scheme with measurement-based encryption technique (MBE-SSP), the result shows that the length of the control key between communicating parties is related to itself security under the fixed-length raw keys. And at the step of quantum key distrubution, the control key is used several times which could causes some raw keys be known by eavesdroper and did not import some interference. So we propose an improved algorithm of MBE-SSP, by increasing the number of the genered rules of control key to reduce the rate for eavesdroper to get measurement base. And we analyze the upper error rate in both orginal scheme and improved scheme based on Breidbart eavedropping\Breidbart resend strategy. The result shows that improved scheme is more sensitive to eavedroper.In the field of quantum signature, a quantum signature scheme is aproposed for multiple people signature situation. Hash function is used to reduce the length of signature information, unitary transformation is used to support multiple user’s signature to the same message and the length of the signature information doesn’t get longer with the increasing number of signatory in the scheme. And the security of the scheme is guaranteed by Heisenberg uncertainty principle and quantum no-cloning theory.