How can it be achieved in designing e-cash based system?
E-cash is essentially an online solution. The buyer must validate the coins by the issuer in order to get the purchase complete. The coins used in the system have the value of the coin, the serial number that is unique for each coin and identity strings connecting the coin to the user withdrawing it. Though, neither the issuer nor the merchant can reduce the identity of the customer by examining the coins if the coin is used only once.