NACO, the "N" Attribute Conformity Checker

Federated identity management enables researchers to access services across organisational bound-
aries using their home institution credentials. However, the success of this model depends on con-
sistent attribute release by Community Authentication and Authorisation Infrastructures (AAIs).
When different Community AAIs release attributes inconsistently, service providers face increased
development complexity, which ultimately threatens the adoption of federated identity in research.
This paper presents NACO (N Attribute COnformity checker), a tool for automated, continuous
validation of attribute compliance against specifications such as AARC-G056. NACO monitors
multiple Community AAIs, validates attribute presence, type correctness, and scoping, and pro-
vides both command-line and REST API interfaces. We describe the design, implementation,
and deployment of NACO across ten European and international Community AAIs, and discuss
findings that have contributed to improved interoperability in federated research infrastructure.