PR.AA-04 focuses on securing identity assertions—digital statements used to convey authentication and user information—across systems like single sign-on or federated environments. This involves protecting assertions with encryption or digital signatures and verifying their integrity to prevent tampering or spoofing. It ensures trust in identity data as it moves between systems.

This subcategory enhances interoperability by adopting standards-based approaches for generating and validating assertions, maintaining security across diverse platforms. It reduces vulnerabilities in identity transmission, safeguarding access to sensitive resources. PR.AA-04 strengthens the reliability of identity management in complex IT ecosystems.