Server-Aided Verification Signatures with Privacy

A server-aided verification signature scheme consists of a digital signature scheme and a server-aided verification protocol. Signatures can be verified by executing the server-aided verification protocol with an untrusted server. In existing server-aided verification signature schemes, the server can learn some information about the message-signature pair to be verified, which is undesirable especially when the message includes some secret information. In this paper, we mainly study the server-aided verification signatures with privacy. Two definitions of privacy for server-aided verification signatures are presented under collusion attacks between the server and the signer. Then based on existing signatures, two concrete server-aided verification signature schemes with privacy are proposed which are both proved secure.