抄録
It has been shown that identity-based encryption with keyword search (IBEKS) can be constructed from level-2 anonymous hierarchical identity-based encryption (A-HIBE). A-HIBE is more complicated than non-anonymous HIBE (NA-HIBE). We have shown the definition of Ciphertext Divided A-HIBE (CD-A-HIBE). The basic idea of CD-A-HIBE is to make it possible to regard NA-HIBE as A-HIBE by dividing ciphertext into two parts so as not to leak the information of identity from the original ciphertext of NA-HIBE. We also have shown a concrete construction of CD-A-HIBEfrom BB1-HIBE, which is one of the NA-HIBE schemes and transformed BB1-CD-A-HIBE to IBEKS whose ciphertext is divided (CD-IBEKS). Then, the computational cost of CD-IBEKS is shown to be often more reasonable than that of IBEKS. In this paper, we show what type of NA-HIBEnot limited to BB1-HIBE can be used for constructing CD-A-HIBEand how to transform a certain type of NA-HIBEto CD-A-HIBE generally. Then, we prove that these CD-A-HIBE schemes have indistinguishability and anonymity. The general transformation from CD-A-HIBEto CD-IBEKS is also shown. We prove that these CD-IBEKS schemes have indistinguishability.
