Attribute-based signcryption provides not only the chance that the participants access the cipher texts by their attributes instead of identities, but also the combined security of confidentiality and unforgeability. An attribute-based signcryption scheme from multi-linear maps was proposed. The circuits presented by Sahai et.al was used as the access structure to support the arbitrary fanout, and the outsourcing computing was employed to reduce the receivers’ computational cost. The security was evaluated in the standard model under the k-decision multi-linear problem assumption. Compared with the existed schemes, the decryptor saved the key communication cost up to 66.7%. Furthermore, the constant cipher texts were kept after being outsourcing computed. The computational cost of the receiver was 8p+(n+3)e.Additionally, this scheme could be verified publicly and gives the foundation of performing secure communication in social networks and others.
