Improved (t,n) Threshold Signature

With the concept of traditional (t,n) threshold signature with truster, a new improved (t,n) threshold signature is proposed combining EIGamal signature and (t,n) threshold signature, in which the privy key is concealed so that the truster could not play the trick. These two signatures are compared, on the base of which it is proved that the new signature can not only be used in group signature not to be deceived by the third person, but also be used in privy work.