Capturing parallel attacks within the data independence framework

We carry forward the work described in our previous papers (Broadfoot et al., 2000, Broadfoot and Roscoe, 2002, and Roscoe, 1998) on the application of data independence to the model checking of cryptographic protocols using CSP and FDR. In particular, we showed how techniques based on data independence could be used to justify, by means of a finite FDR check, systems where agents can perform an unbounded number of protocol runs. Whilst this allows for a more complete analysis, there was one significant incompleteness in the results we obtained: While each individual identity could perform an unlimited number of protocol runs sequentially, the degree of parallelism remained bounded. We report significant progress towards the solution of this problem, by "internalising" all or part of each agent identity within the "intruder" process. We consider the case where internal agents do introduce fresh values and address the issue of capturing the state of mind of internal agents (for the purposes of analysis).