Abstract: To be suitable for the security evaluation of non-interactive deniable authentication protocol,this paper re-defines the attribute of key-compromise impersonation (KCI) as the attribute of sender key-compromise impersonation (SKCI).A new improved scheme is then proposed for solving the receiver KCI problem of Cao's scheme.Compared with the old scheme,the improved scheme saves six times pairing operations and its both sides interactive number of times decreases two times.In addition,the proposed scheme does not need an addition signature,which is necessary in Liao's improved scheme,to provide extra authentication and simultaneously satisfies authenticity,deniability and sender key-compromise impersonation security attributes.