Patent ID: 8442919
Filing Date: 2013-05-14
Classification: G06Q,H04L

Abstract:
1. A method of providing digital cash tokens, the method comprising: providing a user with at least two pairs of keys including a master pair having a private and a public key and at least a pseudonym pair having a private and public key, wherein said master pair is used to authenticate a real identity of a user, said pseudonym pair is used to authenticate a user pseudonym identity, said master pair is not linked with said pseudonym pair and said pseudonym pair is not linked with another pseudonym pair; registering the user known under one or more pseudonyms in a digital cash token issuer; blinding digital signatures based on the master pair of keys for requesting a voucher from a bank, said voucher is blinded by the user and signed by the bank after withdrawing an amount of money from a user account associated with said real identity of the user, wherein the blinding digital signatures is performed by a processing device of the user, and said voucher is usable as a proof of withdrawal of the amount of money from said bank and to request digital cash tokens from a digital cash token issuer; requesting said digital cash tokens using said voucher and said pseudonym pair, said voucher being sent to said bank to check that the voucher has not been used twice, said pseudonym pair is used for authentication without revealing said real identity of the user; issuing digital cash as digital cash tokens from a digital cash token issuer for the user using the voucher, wherein the user is known by the user pseudonym identity; issuing a license from a certificate authority for the pseudonym public key in response to a request that is signed by the master private key of the user; and spending the digital cash tokens using the pseudonym pair of keys.