Informatica

Up to now, there was very little work on studying the revocation problem in existing hierarchical ID-based encryption (HIBE) systems. Certainly, all existing HIBE systems may inherit the revocation method suggested by Boneh and Franklin to revoke illegal or expired users, in which non-revoked users must periodically update their private keys using secure channels by contacting their ancestors in hierarchical structures. In this paper, we propose the first HIBE scheme with public revocation mechanism, called revocable HIBE (RHIBE), which is extended from Lewko and Waters's unbounded HIBE scheme presented in Eurocrypt 2011. We demonstrate that the proposed RHIBE scheme is fully secure while removing the requirement of secure channels for private key updating in Boneh and Franklin's revocation method. The public revocation mechanism is an exciting alternative to the existing revocation methods. Finally, we discuss the transformation technique from a HIBE scheme to a RHIBE scheme and employ it to another well-known HIBE scheme.