Parameter Usage Parameter Usage K The order of G1 and G2 Kpub,o The O’s public key G1 The cyclic group with operation “+” H1 The hash function used to derive one’s ID to its public key G2 The cyclic group with operation “×” H2 The hash function used to derive the output of the Bilinear Pairing function ê to a symmetric key ê The Bilinear Pairing function H3 The hash function used to generate the electronic means

Table 1: The Usage of the Parameters In public-params Set.