Directed Signatures and Application

This paper presents a directed (or designated-receiver) signature scheme with the property that the signature can be veriied only with the help of the signature receiver. Such signatures are intended to protect the privacy of the signature receiver in applications where the signed message contains information personally sensitive to the receiver. We also present its application to shared veriication of signatures and threshold cryptosystems. The resulting group-oriented cryptosystems are fully dynamic and scalable.