Technical Report 2005-004

A Fully Abstract Encoding of the pi-Calculus with Data Terms

Michael Baldamus, Joachim Parrow, and Björn Victor

February 2005

The pi-calculus with data terms (piT) extends the pure pi-calculus by data constructors and destructors and allows data to be transmitted between agents. It has long been known how to encode such data types in pi, but until now it has been open how to make the encoding fully abstract, meaning that two encodings (in pi) are semantically equivalent precisely when the original piT agents are semantically equivalent. We present a new type of encoding and prove it to be fully abstract with respect to may-testing equivalence. To our knowledge this is the first result of its kind, for any calculus enriched with data terms. It has particular importance when representing security properties since attackers can be regarded as may-test observers. Full abstraction proves that it does not matter whether such observers are formulated in pi or piT, both are equally expressive in this respect. The technical new idea consists of encoding data as table entries rather than active processes, and using a firewalled central integrity manager to ensure data security.

Note: Updated April 2005

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