Cryptographic approch for workflow systems

Abstract

This paper proposes encryption schemes to enforce the order of the procedure in a workflow system. In workflow systems, it is important to perform a procedure according to an order that is given by some regulation. In addition, it is desired that each reviewer checks a necessary part of a document to admit the application because the document sometime contains privacy information, e.g., name, birthday, income and so on. There is a procedure in a workflow system which it is sufficient to pass if one of two reviewers admits the document. More generally, there is a procedure in a workflow system that can be passed if k of n reviewers admit the document, which we call a "threshold procedure". By applying a cryptographic technique, e.g., a multiple encryption and secret sharing, this paper gives a method to realize various procedures in workflow systems, i.e., controlling the order of reviewers, disclosing a part of document selectively, and a threshold procedure. Conventional workflow systems control their procedure by a server, which we consider a trusted one. This implies that an administrator might tamper a procedure. The proposed schemes help us to enforce a procedure even if he/she is not trustworthy. © 2008 International Federation for Information Processing.