Question about integrity of Blind Signature

Hi! I have some question about ecash protocol. In ecash protocol, we represent money by a sequence number which is signed by bank. And for privacy, we use blind signature. But when we send bank a pesudo sequence number-- X*PK(r) (X:sequence number we want, r :random number to cheat bank) then we can get SK(X*PK(r)) from bank, and get money by SK(X*PK(r))/r=SK(X). But if we divide SK(X*PK(r)) with r', we can get another money? It confuses me. How does it preserve the integrity of the money, and let people divide r on the SK(X*PK(r)) ? It confuses me very long time. Thanks for any help! Chein-hsin Liu 4/1/96