If the public key is publicly accessible, then everybody can verify the signature, while only the signer, who knows the private key, is able to sign. Acknowledgements We would like to thank H. P . Frei, T. Kofler , and U. Maurer for valuable comments. We begin with the RSA algorithm. In many systems the protection of the user s privacy relies exclusively on administrative and legal measures.
Payments are anonymous and different payments of the same customer are unlinkable.
In this paper the customer is male whereas the judge is female. Blind signature systems . In most presently used payment systems the protection of the user s privacy relies exclusively on administrative and legal measures. Furthermore, the customer may require that his privacy be protected. Blind signature systems .