Hierarchical conditional proxy re-encryption

In this paper, we introduce a new primitive called hierarchical conditional proxy re-encryption (HC-PRE) that enhances the concept of C-PRE by allowing more general re-encryption key delegation patterns. Hierarchical conditional proxy re-encryption (HC-PRE) scheme is the hierarchical extension of conditional proxy re-encryption (C-PRE) where the condition is a vector of keywords. We present an efficient construction of hierarchical key derivation C-PRE scheme where the ciphertext length is independent from the depth of the hierarchy. We further extend our work by presenting a more generalized key delegation, by allowing the use of a wildcard in the keyword vector. (C) 2012 Elsevier B.V. All rights reserved.