An auditing scheme is a good way to prove owner＇s data outsourced to the cloud are kept intact, and a scheme capable of giving public verifiability service is a good option that some researchers have managed to build for the last few years. However, in a public auditing scheme everybody does verification of data and a possibility of leaking some secrete information to the public verifiers is an issue that data owners are unhappy with this scenario. For example, the data owner does not want anybody else to know he has the data stored in the cloud server. Motivated by the issue of privacy associated with public auditing system, we proposed a designated verifier auditing （DVA） scheme based on Steinfeld et al.＇s universal designated verifier （DV） signature scheme. Our DVA scheme authorizes a third party auditor with private verification capability. It provides private verification because the scheme involves private key of the verifier. Moreover, we present the batch auditing scheme to improve auditing efficiency. Through rigorous security analysis we showed that our scheme is provably secure in the random oracle model assuming that the computational Diffie-Hellman （CDH） problem is hard over the group of bilinear maps.
A quantum broadcast communication and authentication protocol with a quantum one-time pad based on the Greenberger-Horne-Zeilinger state is proposed. A binary string is used to express the identity of the receiver, which is encoded as a single sequence of photons. The encoded photon sequence acts as a detection sequence and implements au- thentication. An XOR operation serves as a one-time pad and is used to ensure the security of the protocol. The binary string is reused even in a noisy channel and proves to be unconditionally secure. In contrast with the protocols proposed by Wang et al. [Chin. Phys. 16 1868 （2007）] and Yang et al. [Chin. Phys. B 19 070304 （2010）], the protocol in this study implements the identity authentication with a reusable binary string; no hash function or local unitary operation is used. The protocol in this study is also easier to implement and highly efficient without losing security.
A quantum secure direct communication and authentication protocol is proposed by using single photons.An information transmission is completed by sending photons once in quantum channel,which improves the efficiency without losing the security.The protocol encodes identity-string of the receiver as single photons sequence,which acts as detection sequence and implements authentication.Before secret message is encoded as single photons sequence,it is encrypted with identity-string of the sender by using XOR operation,which defends quantum teleportation attack efficiently.The base identity-strings of the sender and the receiver are reused unconditionally secure even in noisy channel.Compared with the protocol proposed by Wang et al.(Phys Lett A,2006,358:256–258),the protocol in this study sends photons once in one transmission and defends most attacks including‘man-in-the-middle’attack and quantum teleportation attack efficiently.
