On blind signatures and perfect crimes

David Chaum has introduced the idea of blind signatures, an extension of the concept of digital signatures, as a way to protect the identity and privacy of a user in electronic payment and service networks. Blind signatures also prevent so-called "dossier creation" about users by organizations. While the concept of blind signatures still allows authorities to distinguish between valid and false data, it prevents these authorities from connecting specific data or actions to specific users. With the growing emphasis on the protection of the privacy of user data and user actions in electronic systems, blind signatures seem to be a perfect solution. This paper however, discusses a problematic aspect of blind signatures, showing that this perfect solution can potentially lead to perfect crime. We use a real crime case as an example.