Process calculi are expressive specification languages for concurrency. They have been very successful in two research strands: (a) the analysis of security protocols and (b) the enforcement of correct message-passing programs. Despite their shared foundations, languages and reasoning techniques for (a) and (b) have been separately developed. Here we connect two representative calculi from (a) and (b): we encode a (high-level) $$\pi $$-calculus for multiparty sessions into a (low-level) applied $$\pi $$-calculus for security protocols. We establish the correctness of our encoding, and we show how it enables the integrated analysis of security properties and communication correctness by re-using existing tools.