This paper defines the \u201cultimate\u201d formal semantics for Alice and Bob notation, i.e., what actions the honest agents have to perform, in the presence of an arbitrary set of cryptographic operators and their algebraic theory. Despite its generality, this semantics is mathematically simpler than any previous attempt. For practical applicability, we introduce the language SPS and an automatic translation to robust real-world implementations and corresponding formal models, and we prove this translation correct with respect to the semantics
