  Many anonymous communication networks (ACNs) with different privacy goals
have been developed. However, there are no accepted formal definitions of
privacy and ACNs often define their goals and adversary models ad hoc. However,
for the understanding and comparison of different flavors of privacy, a common
foundation is needed. In this paper, we introduce an analysis framework for
ACNs that captures the notions and assumptions known from different analysis
frameworks. Therefore, we formalize privacy goals as notions and identify their
building blocks. For any pair of notions we prove whether one is strictly
stronger, and, if so, which. Hence, we are able to present a complete
hierarchy. Further, we show how to add practical assumptions, e.g. regarding
the protocol model or user corruption as options to our notions. This way, we
capture the notions and assumptions of, to the best of our knowledge, all
existing analytical frameworks for ACNs and are able to revise inconsistencies
between them. Thus, our new framework builds a common ground and allows for
sharper analysis, since new combinations of assumptions are possible and the
relations between the notions are known.
