Outsourced Attribute-Based Signcryption in the Cloud Computing

An Attribute-Based Signcryption is a natural extension of attribute-based encryption and attribute-based signature where we have the message confidentiality and authenticity together. However, due to the high expressiveness of ABE policies the computational complexities of ABE key issuing and decryption are getting prohibitively high and the heavy computational cost is required during the signing in existing work of ABS which grows linearly with the size of the predicate formula. This presents a significant challenge for resource-limited users (such as mobile devices)to perform such heavy computation independently. In order to solve the above challenge, we propose a new outsourced attribute based signcryption scheme which supports both outsourced key issuing and decryption in ABE and reduce the signing computational overhead at user side in ABS and also it is used to outsource the partial verification to reduce computational overload to the receiver side. We formally prove the security of the newly proposed scheme in the random oracle model.