Formal, symbolic techniques for modelling and automatically analyzing
security protocols are extremely successful and were able to discover
many security flaws. Initially, these techniques were mainly developed
to analyze authentication and confidentiality properties. Both these
properties are trace properties and efficient tools for their
verification exist. In more recent years anonymity-like properties have
received increasing interest. Many flavors of anonymity properties are
naturally expressed in terms of indistinguishability and modeled as an
observational equivalence in process calculi. We will present recent
advances in the verification of such indistinguishability properties and
illustrate their usefulness on examples from electronic voting and
RFID protocols.