Identity-Based Encryption with Non-Interactive Key Update
Cryptology ePrint Archive, Report 2004/338, (2004)Abstract
In this paper, we discuss non-interactive updating of private keys
in identity-based encryption (IBE). IBE is a public key cryptosystem
where a public key is an arbitrary string. Key revocation in IBE,
in practice, is unavoidable and also a problem that cannot be bypassed.
Our main contribution of this paper is to propose a novel constructions
of IBE in which the private key is renewed without having to make
any changes to its public key, i.e. user's identity. We achieve this
by extending the hierarchical IBE (HIBE). Regarding security, in
addition to chosen ciphertext attack, we address semantic security
for a very strong attack environment which models all possible types
of key exposures in the random oracle model. Straightforward extension
of the HIBE, however, is completely insecure for such an attack model.
Moreover, we show a method of constructing (partially collusion resistant)
HIBE from arbitrary IBE in the random oracle model. By the combination
of this method and the technique used in the above scheme we can
construct an IBE with non-interactive key update from an arbitrary
IBE.