Provably Secure Blind Signature Schemes

In this paper, we give a provably secure design for blind signatures, the most important ingredient for anonymity in off-line electronic cash systems. Previous examples of blind signature schemes were constructed from traditional signature schemes with only the additional proof of blindness. The design of some of the underlying signature schemes can be validated by a proof in the so-called random oracle model, but the security of the original signature scheme does not, by itself, imply the security of the blind version. In this paper, we first propose a definition of security for blind signatures, with application to electronic cash. Next, we focus on a specific example which can be successfully transformed in a provably secure blind signature scheme.