How can non-repudiation be achieved into designing e-cash based system?

E-cash is fundamentally an online solution. The buyer should validate the coins by the issuer so as to get the purchase completed. The coins used within the system comprise the value of the coin, the serial number which is unique for each coin and identity strings connecting the coin to the user withdrawing this. Conversely, neither the issuer nor the merchant can infer the identity of the customer by examining the coins when the coin is used only once.

The user of the e-cash system should have an account into a bank which is a certified eCash minter. The secret splitting and blind signature techniques are used, which makes sure that the coins are anonymous till used twice. The appropriate algorithm is RSA and DES.