A novel proxy signature scheme based on user hierarchical access control policy

In this paper, we propose a new security protocol for proxy signature by a hierarchy of proxy signers. In this protocol, the original signer delegates his/her signing capability to a predefined hierarchy of proxy signers. Given the documents of a security class to be signed by the original signer, our scheme suggests a protocol for the hierarchy of proxy signers to sign the document on behalf of the original signer. The concept of hierarchical access control limits the number of people who could sign the document to the people who have the required security clearances. User in a security class requires two secret keys: one which identifies his/her security clearance, and that can also be derived by a user of upper level security clearance and second is his/her private key which identifies him/her as a proxy signer for the signature generation. We show that our scheme is efficient in terms of computational complexity as compared to the existing related proxy signature schemes based on the hierarchical access control. Our scheme also supports addition and deletion of security classes in the hierarchy. We show through security analysis that our scheme is secure against possible attacks. Furthermore, through the formal security analysis using the AVISPA (Automated Validation of Internet Security Protocols and Applications) tool we show that our scheme is also secure against passive and active attacks.