Anonymous offline digital cash scheme Can a digital cash scheme exist that is anonymous and offline using blind signature and anonymous signature?
Blind signatures are online by definition. They involve at least two independent parties that interact during the signature generation process. A protocol is "online" if a successful execution of the protocol requires an exchange of messages between two or more independent parties. Consequently, no application of blind signatures, including a digital cash system, can be completely offline.

Furthermore, any transaction within a digital cash system has to be, to some extent, completed "online". "Digital cash" refers to a system that allows you to complete a transaction by exchanging nothing more than information and in which, somehow, your credits are stored digitally on your device. Your digital cash can't be spent without access to the digital information only you possess.

This means, firstly, that each potential owner of credits in a digital cash system has to appear as a black box to any other potential owner of credits within the same system. The only requirement is that each potential credit owner is able to play out the protocol steps involved in a transaction. There is no way for one party to digitally verify that another party is using specific hardware or software that guarantees that the other party is not tampering with audit trails of transactions that have never been committed to any other party.

With logical necessity: If you want to pay someone some amount, you have to communicate this somehow to someone, or else there will be no transaction. You cannot commit to a transaction if you keep all records of the transaction to yourself, because in such case you could simply delete those records at a later time, and there would be no way for anyone to know that the transaction had ever taken place.