Cryptanalysis of an (hierarchical) identity based parallel key-insulated encryption scheme

Recently, Ren and Gu (2010) proposed an identity-based parallel key-insulated encryption (IBPKIE) scheme, and further extended their IBPKIE scheme to a hierarchical identity-based parallel key-insulated encryption (HIBPKIE) scheme. They claimed that both schemes are secure against adaptive chosen-ciphertext attacks without random oracles. However, in this paper, by giving concrete attacks, we indicate that their schemes are even not secure against chosen-plaintext attacks.