High Quality Content by WIKIPEDIA articles! Using cryptography, ecash was introduced by David Chaum as an anonymous electronic cash system. He used blind signatures to achieve unlinkability between withdrawal and spend transactions. Depending on the properties of the payment transactions, one distinguishes between on-line and off-line electronic cash. The first off-line e-cash system was proposed by Chaum and Naor. Like the first on-line method, it is based on RSA blind signatures.