Abstract
Recently-introduced Publicly Posted Composite Documents (PPCDs) enable composite documents with different formats and differential access control to participate in cross-organizational workflows distributed over potentially non-secure channels. The original PPCD design was based on a. Public Key Infrastructure, requiring each workflow participant to own a. pair of public and private keys. This solution also required the document master to know the corresponding valid public keys (certificates) of all participants prior to commencement of the workflow. Using Identity Based Encryption (IBE), a recently described cryptographic technique, we eliminate the requirement for the prior knowledge and distribution of the workflow participants' keys. The required public keys for each workflow participant are calculated based on user identities and other relevant factors at workflow onset. The generation of corresponding private keys can be delayed up until the workflow step, when the corresponding workflow participants require access to the document. The solution presented provides automatic workflow order enforcement and the ability to impose multiple document release dates real-time.