  Next generation mobile networks are poised to transition from monolithic
structures owned and operated by single mobile network operators into
multi-stakeholder networks where various parties contribute with
infrastructure, resources, and services. However, a federation of networks and
services brings along a crucial challenge: Guaranteeing secure and trustworthy
access control among network entities of different administrative domains. This
paper introduces a novel technical concept and a prototype, outlining and
implementing a 5G Service-Based Architecture that utilizes Decentralized
Identifiers and Verifiable Credentials instead of traditional X.509
certificates and OAuth2.0 access tokens to authenticate and authorize network
functions among each other across administrative domains. This decentralized
approach to identity and permission management for network functions reduces
the risk of single points of failure associated with centralized public key
infrastructures. It unifies access control mechanisms and lays the groundwork
for lesser complex and more trustful cross-domain key management for highly
collaborative network functions in a multi-party Service-Based Architecture of
6G.
