GO-CP-ABE:group-oriented ciphertext-policy attribute-based encryption

We introduce a variant of ciphertext-policy attribute-based encryption called group-oriented ciphertext-policy attribute-based encryption (GO-CP-ABE). In the new notion, message is encrypted under an access structure over attributes and users are described by their attributes. In addition, users are divided into different groups and each user belongs to only one group. Users within the same group can merge their attributes to decrypt successfully, if the union of their attributes satisfies the access structure embedded in the ciphertext. But users from different groups cannot realise this cooperative decryption. We define the security model of GO-CP-ABE and present an efficient design by revising an existing CP-ABE scheme.