Central Authentication Service (CAS)
A legacy SSO protocol (Yale University) that allows users to authenticate once and access multiple web applications.
What is Central Authentication Service (CAS)?
Central Authentication Service (CAS) is a legacy single sign-on (SSO) protocol originally developed at Yale University in 2002. CAS allows users to authenticate once to a central CAS server and then access multiple web applications without re-entering credentials. While popular in higher education (universities), CAS is being replaced by modern SSO protocols: SAML 2.0 and OpenID Connect (OIDC). CAS uses a simple ticket-based system where applications validate service tickets against the CAS server.
Analogy
Think of CAS like a university's student ID card that gets you into the library, gym, cafeteria, and dorms with a single swipe. Once you're authenticated (registered student), you can access all campus services without re-proving who you are.
Types and Use Cases
CAS Components:
- CAS Server: Central authentication server (validates credentials, issues tickets)
- CAS Client: Applications that integrate with CAS (validate tickets)
- Service Ticket (ST): Short-lived token issued after authentication
- Ticket Granting Ticket (TGT): Long-lived session token for multiple STs
Common Use Cases:
- Higher Education: Universities with legacy systems (Blackboard, library systems)
- Legacy Enterprise Apps: Older Java/.NET applications with CAS support
- Internal Portals: Employee portals with multiple internal tools
- Migration Projects: Legacy CAS to modern SAML/OIDC transitions"
How it Works
{
"casFlow": {
"version": "3.0",
"authentication": {
"casServer": "https://sso.university.edu/cas",
"credentials": "username/password",
"tgt": "TGT-12345-abc"
},
"serviceAccess": {
"service": "https://library.university.edu",
"serviceTicket": "ST-67890-xyz",
"validationUrl": "https://sso.university.edu/cas/serviceValidate"
}
}
}Central Authentication Service (CAS) vs SAML 2.0
Central Authentication Service (CAS)
SAML 2.0
CAS uses simple ticket-based system,
SAML uses XML assertions (more complex)
CAS is legacy (2002),
SAML 2.0 is modern standard (2005, widely adopted)
CAS has limited attributes (basic user info),
SAML supports rich attribute assertions
Best Practices for Central Authentication Service (CAS)
- Plan Migration: If using CAS, plan migration to SAML 2.0 or OIDC for better security and features"
- Secure Ticket Validation: Always validate STs server-to-server (not client-side) to prevent interception"
- Use HTTPS Everywhere: CAS tickets can be intercepted if not using TLS/HTTPS"
How LoginRadius Powers Central Authentication Service (CAS)
LoginRadius CIAM platform is a modern alternative to legacy CAS implementations. Our platform provides SAML 2.0 and OpenID Connect federation - not legacy CAS. LoginRadius offers Service Provider (SP) capabilities for SAML/OIDC, rich attribute mapping, JIT provisioning, single logout, and comprehensive audit logs. We also provide migration tools and consulting to help you transition from legacy CAS to modern SSO protocols.
FAQs
CAS is considered legacy technology. Most organizations are migrating to SAML 2.0 or OpenID Connect (OIDC) which offer better security, mobile support, and modern architecture. CAS is still found in some universities and legacy enterprise applications. New projects should use SAML or OIDC instead of CAS.
CAS is a simple ticket-based protocol (2002) primarily for web apps. Modern SSO (SAML/OIDC) supports web, mobile, APIs, and offers richer features: single logout, attribute assertions, and federation. LoginRadius recommends SAML 2.0 or OIDC for new projects instead of legacy CAS.
LoginRadius is a modern CIAM platform that supports SAML 2.0 and OpenID Connect - not legacy CAS. Our platform provides SSO for web, mobile, and APIs with rich attribute mapping, JIT provisioning, and modern security features. LoginRadius also provides migration tools to help you move from legacy CAS to modern SAML/OIDC federation.