Non-interactive confirmer signatures

Abstract

The study of non-transferability of digital signatures, such as confirmer signatures, has enjoyed much interest over the last twenty years. In PKC '08, Liskov and Micali noted that all previous constructions of confirmer signatures consider only offline untransferability - non-transferability is not preserved if the recipient interacts concurrently with the signer/confirmer and an unexpected verifier. We view this as a result of all these schemes being interactive in the confirmation step. In this paper, we introduce the concept of non-interactive confirmer signatures (which can also be interpreted as extractable universal designated-verifier signatures). Non-interactive confirmer signatures give a neat way to ensure the online untransferability of signatures. We realize our notion under the "encryption of a signature" paradigm using pairings and provide a security proof for our construction without random oracles. © 2011 Springer-Verlag Berlin Heidelberg.