Designated Verifier Signature Transformation: A New Framework for One-Time Delegating Verifiability

Designated verifier signature (DVS) is a variant of digital signature which can designate a verifier to verify signatures. The main difference between message authentication code and DVS is that no shared key is initially set in DVS. In this paper, we propose a new notion, designated verifier signature transformation (DVST), which allows a cloud server to convert a DVS to a multi-designated verifier signature (MDVS) as long as the original verifier provides a token to the server. For more flexible use, the converted signature can support verification with more than threshold number of designated verifiers. Accordingly, a specific security definition is formalized as token unforgability. Our construction is proposed and built from bilinear map with security analysis.