A revocable group signature scheme with the property of hiding the number of revoked users

Abstract

If there are many displaced workers in a company, then a person who goes for job hunting might not select this company. That is, the number of members who quit is quite negative information. Similarly, in revocable group signature schemes, if one knows (or guesses) the number of revoked users (say r), then one may guess the reason behind such circumstances, and it may lead to harmful rumors. However, no previous revocation procedure can achieve to hide r. In this paper, we propose the first revocable group signature scheme, where r is kept hidden. To handle these properties, we newly define the security notion called anonymity w.r.t. the revocation which guarantees the unlinkability of revoked users. © 2012 Springer-Verlag.