Attribute-Based Signcryption Scheme with Non-monotonic Access Structure

The encrypted data presented by the traditional public key cryptosystem only provides the access control of nothing or all, that is, one can either decrypt the entire plaintext or nothing other than its length. Attribute-Based Signcryption provides not only the combined confidentiality and unforgeability, but also the chance that the participants access the cipher texts by their attributes instead of identities. The paper proposed a new attribute based signcryption scheme, which has the non-monotonic access structure and constant-size cipher text. The proposal supports the AND, OR, and NEG gate, and provides the more flexible access control and express ability. The security in confidentiality and unforgeability, are evaluated in the standard model under the q-DBDHE assumption. By employing the zero inner-multiplication, the length of the cipher text has no related with the number of attributes and lies in 5|G1|+|m| constantly. In additionally, the scheme could be verified publicly. It could be used in massive social network and makes the chance that sharing the data between communities.