Which open standard underpins OpenID Connect, enabling Cisco Duo to authorize application access?

OAuth 2.0 is the authorization framework on which OpenID Connect adds an identity and authentication layer. An OpenID Connect client uses OAuth-style authorization requests and token endpoints, while the additional ID token carries authenticated identity claims. Cisco Duo supports OIDC-based integrations in which OAuth access tokens authorize access to protected applications or services. Therefore, A is correct. SCEP provides certificate-enrollment services and is unrelated to application authorization. RSTP prevents Layer 2 switching loops. Kerberos provides ticket-based authentication within a trusted realm but does not underpin OpenID Connect. OAuth 2.0 supplies the authorization foundation that OpenID Connect extends for federated authentication and identity communication. OpenID Connect Core specification

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