Fair Blind Signatures
Markus Stadler and Jean-Marc Piveteau and Jan Camenisch
A blind signature scheme is a protocol allowing to get a signature
from a signer such that the signer's view of the protocol cannot be
linked to the resulting message-signature pair. Blind signature
schemes are used in anonymous digital payment systems. Since the
existing proposals of blind signature schemes provide perfect
unlinkability, such payment systems could be misused by criminals,
e.g. to safely obtain a ransom or to launder money. In this paper,
a new type of blind signature schemes is proposed, called fair blind
signature schemes. They have the additional property that a trusted
entity can deliver information allowing the signer to link his view
of the protocol and the message-signature pair. Two types of fair
blind signature schemes are distinguished and several realizations
are presented.