Research Of Multi-authority Attribute-based Signcryption

In view of the problems existing in the cloud storage service scenario,and the limitations of the Attribute-based encryption scheme,this topic organically integrates Attribute-based encryption and Attribute-based signature to form an Attribute-based signcryption system,so as to meet the four basic security requirements of data.In addition,the existing Attribute-based signcryption schemes are not suitable for cloud storage service scenarios with multiple authorities.Therefore,this thesis is committed to construct an efficient and secure Attribute-based signcryption scheme in the scenario of multiple authorities.The main research work and contribution of this thesis include the following two aspects.In this thesis,we construct an Attribute-based signcryption scheme for the scenario of multiple authorities.This scheme achieves the constant size of ciphertext.Compared with the existing schemes,this scheme has obvious advantages in communication cost.In terms of function,the scheme provides signer privacy protection,so that any entity can not directly obtain the attribute set related to signer’s signature key through ciphertext.Meanwhile,the scheme also provides public verifiability,so that the cloud storage server can verify the validity of the ciphertext without decryption key.In the aspect of security,the scheme is proved under the random oracle model,which meets the two security requirements of data confidentiality and ciphertext unforgeability.Aiming at the problems of user logout and user key abuse in cloud storage environment,this thesis constructs an Attribute-based signcryption scheme which provides the functions of user/attribute revocation and user tracking.Meanwhile,the user tracking function can locate the system users who leak the key,providing data support for the user revocation function.In this thesis,the two schemes are compared with the similar schemes by means of theory and simulation experiment,and the comprehensive analysis is carried out from the perspective of performance,functionality and safety,which proves the feasibility and innovation of the scheme.