An Efficient Solution for Time-Bound Hierarchical Key Assignment Scheme

Abstract

Time-bound hierarchical key assignment (TBHKA) scheme is a cryptographic method. It can assign encryption keys depending on time to a set of security classes in a partially ordered hierarchy. Only the authorized user can compute the encryption key to access the subscribing class (including lower down class) according to the hierarchy. In 2005, Yeh firstly proposed a RSA-based TBHKA scheme supporting discrete time period. However, it had been proved insecure against user colluding attacks. Up to now, there are less study for TBHKA scheme supporting discrete time period. In this paper, we propose a secure and efficient TBHKA scheme. Our scheme is based on pairing-based public key cryptosystem and supports discrete time period. The security analysis is demonstrated that our scheme is secure against outside adversary and malicious user. Finally, we make comparisons between recently proposed two TBHKA schemes and our scheme. It will show the advantages of our scheme.