Figure 7: An UML Activity Diagram for the resolution of policy violation
Figure 7 presents the protocol for the policy violation resolution process. When an unauthorized copy of document, say X”, is found, the affected document provider can extract the unique request identifier V encoded in X”. Based on the corresponding request record in its authorization database, the document provider retrieves the permutation function σ, its signed hashed value Sign(H(σ)), and the intelligence user certificate containing EK(W) and K. The document provider submits these evidences to a judge for an allegation made against a user. In our approach, the judge can carry out the verification directly without the need of approaching the suspected document user for the watermark. This is a desirable feature because the document user might either provide a wrong watermark or have lost the watermark upon the allegation. In our protocol, if the watermark EK(σW) can be detected in the encrypted version of unauthorized copy EK(X”), the suspected document user is concluded guilty; otherwise innocent.