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In order to satisfy the requirements of long-distance multi-node quantum networks，two multi-party controlledquantum communication protocols are put forward via maximally and partially entangled quantum channels.For the maximally entangled channels,projective measurements are used to realizemulti-party controlled joint remote preparation of an arbitrary four-qubitX-state.For the partially entangled channels,collective unitary operations and optimal positive operator-valued measures are used to realize multi-party controlled joint remote preparation of an arbitrary four-qubitX-state.The theoretical analysis shows that the efficiency of the first scheme can be up to 100% which is suprior to that of others.In addition,the efficiency of the second scheme is effectively improved and the way to be used to construct two kinds of measurement methods can be utilized in the similar protocols.

In order to satisfy the requirements of long-distance multi-node quantum networks，two multi-party controlledquantum communication protocols are put forward via maximally and partially entangled quantum channels.For the maximally entangled channels,projective measurements are used to realizemulti-party controlled joint remote preparation of an arbitrary four-qubitX-state.For the partially entangled channels,collective unitary operations and optimal positive operator-valued measures are used to realize multi-party controlled joint remote preparation of an arbitrary four-qubitX-state.The theoretical analysis shows that the efficiency of the first scheme can be up to 100% which is suprior to that of others.In addition,the efficiency of the second scheme is effectively improved and the way to be used to construct two kinds of measurement methods can be utilized in the similar protocols.

Multi-party concurrent signatures were first proposed by Tonien et al at ISC2006,but Xie and Tan pointed Tonien et al's scheme doesn't satisfy fairness and they reconstructed multi-party concurrent signature schemes respectively.Through analysis,the multi-party concurrent signature schemes proposed by Xie and Tan don't satisfy fairness either,so a formal security model of fair multi-party concurrent signatures was proposed and a multi-party concurrent signature scheme based on bilinear pairing and multi-party key agreement was also reconstructed.Analysis shows that the new scheme satisfies correctness,unforgeability,ambiguity,concurrency and fairness in the random oracle model assuming the CDH problem is intractable and highly efficient in signature size,computation cost and communication cost compared with other schemes of its kind.

Multi-party concurrent signatures were first proposed by Tonien et al at ISC2006,but Xie and Tan pointed Tonien et al's scheme doesn't satisfy fairness and they reconstructed multi-party concurrent signature schemes respectively.Through analysis,the multi-party concurrent signature schemes proposed by Xie and Tan don't satisfy fairness either,so a formal security model of fair multi-party concurrent signatures was proposed and a multi-party concurrent signature scheme based on bilinear pairing and multi-party key agreement was also reconstructed.Analysis shows that the new scheme satisfies correctness,unforgeability,ambiguity,concurrency and fairness in the random oracle model assuming the CDH problem is intractable and highly efficient in signature size,computation cost and communication cost compared with other schemes of its kind.