A company wants to rely on another platform for authorization. What is the best approach to implement this?

In the context of relying on another platform for authorization, using OAuth is the most appropriate choice. OAuth is an open standard for access delegation commonly used to grant third-party applications limited access to user resources without exposing their credentials. It allows a user to authorize a third-party application to access their information on behalf of the user, making it an excellent fit for scenarios where multiple platforms need to communicate and authorize user access.

While TACACS+ and RADIUS are both protocols focused on network access authentication and can offer some level of authorization, they are more suited for validating user credentials for system access rather than managing authorizations across different platforms. SAML (Security Assertion Markup Language) is also an important standard, particularly for Single Sign-On (SSO), and it facilitates identity federation, but it primarily focuses on authentication rather than authorization.

Given the goal is to implement a robust authorization solution that allows reliance on another platform, OAuth stands out as the best approach.