  Trust-building mechanisms among network entities of different administrative
domains will gain significant importance in 6G because a future mobile network
will be operated cooperatively by a variety of different stakeholders rather
than by a single mobile network operator. The use of trusted third party issued
certificates for initial trust establishment in multi-stakeholder 6G networks
is only advisable to a limited extent, as trusted third parties not only
represent single point of failures or attacks, but they also cannot guarantee
global independence due to national legislation and regulatory or political
influence. This article proposes to decentralize identity management in 6G
networks to enable secure mutual authentication between network entities of
different trust domains without relying on a trusted third party and to empower
network entities with the ability to shape and strengthen cross-domain trust
relationships by the exchange of verifiable credentials. A reference model for
decentralized identity management in 6G is given as an initial guide for the
fundamental design of a common identity management system whose operation and
governance are distributed equally across multiple trust domains of
interconnected and multi-stakeholder 6G ecosystems.
