  This paper presents a comprehensive classification of identity management
approaches. The classification makes use of three axes: topology, type of user,
and type of environment. The analysis of existing approaches using the
resulting identity management cube (IMC) highlights the trade-off between user
control and trust in attributes. A comparative analysis of IMC and established
models identifies missing links between the approaches. The IMC is extended by
a morphology of identity management, describing characteristics of cooperation.
The morphology is then mapped to the life cycle of users and identity
management in a further step. These classifications are practically underlined
with current approaches. Both methods combined provide a comprehensive
characterization of identity management approaches. The methods help to choose
suited approaches and implement needed tools.
