anonymity(key-privacy) as well as security(data-privacy) is useful and widely desired.Recently Canetti-Halevi-Katz proposed a generic and elegant IBE-based construction for(tra-ditional) public-key encryption
whose performance was improved by another construction proposed by Boneh-Katz.To analyze such two constructions’ anonymity
two new and generic concepts in IBE scheme
"master-key anonymity"and"relevant master-key anonymity"were proposed and two different sufficient conditions for chosen-ciphertext anonymity were proved for Canetti-Halevi-Katz and Boneh-Katz constructions.