Abstract: We analyze the security of the three m out of n oblivious transfer schemes proposed by Y.Mu et al, and then point out the insecurities of their schemes. We also provide our improvements on them respectively, which prevent users from getting more messages or disobeying the protocol. One of the improved schemes is more efficient than all the schemes proposed by Y.Mu et al.

Key words: oblivious transfer, security analysis, improved protocol