Efficient Lattice HIBE in the Standard Model with Shorter Public Parameters

The concept of identity-based cryptosystem was introduced by Adi Shamir in 1984. In this new paradigm users’ public key can be any string which uniquely identifies the user. The task of Public Key Generator (PKG) in IBE is to authenticate identity of the entity, generate the private key corresponding to the identity of the entity and finally transmit the private key securely to the entity. In large network PKG has a burdensome job. So the notion of Hierarchical IBE (HIBE) was introduced in [11,12] to distribute the workload by delegating the capability of private key generation and identity authentication to lower-level PKGs. In Eurocrypt 2010 Agrawal et al [1] presented an efficient lattice based secure HIBE scheme in the standard model in weaker security notion i.e. selective-ID. Based on [1], Singh et al [18] constructed adaptive-ID secure HIBE with short public parameters and still the public parameters is very large (total

l

′′×

h

 + 2 matrices). In this paper, we have reduced the size of the public parameters from

l

′′×

h

 + 2 matrices to

l

′′ + 2 matrices using Chatterjee and Sarkar’s [8] and blocking technique [7], where

h

is the number of levels in HIBE.