Book excerpt: ProVerif is an automatic symbolic protocol verifier. It supports a wide range of cryptographic primitives, defined by rewrite rules or by equations. It can prove various security properties: secrecy, authentication, and process equivalences, for an unbounded message space and an unbounded number of sessions. It takes as input a description of the protocol to verify in a dialect of the applied Pi calculus, an extension of the Pi calculus with cryptography. It automatically translates this protocol description into Horn clauses and determines whether the desired security properties hold by resolution on these clauses. This survey presents an overview of the research on ProVerif.