Electronic cash system based on anonymous coins have been invented by David Chaum. However, von Solms and Naccache discovered that such anonymous coins also very well suited to support criminals in Blacoailing. In this paper, we suggest a method that a client informs a bank of the information about blackmailing attack by using Schnorr identification protocol of XTR version at the stage of identification, whenever he is blackmailed. In general, blackmailing is the most serious among the various drawbacks of electronic cash system. Especially, blackmiling to be done when the client is kidnapped brings a fatal result to electronic cash system. But if the Schnorr identification protocol of XTR version is used, we can efficiently defeat blackmailing without assumption required in the existing method to defeat blackmailing.