The evolution of authentication for computer systems and the web, a trend from simple, local authentication methods to more complex, distributed, and secure systems that can handle the demands of modern web applications and services.

1. Early days (1960s-1970s):

   • Simple username and password systems
   • Primarily used in mainframe environments
   • Limited to local, physical access

2. 1980s:

   • Introduction of personal computers
   • Rise of network-based authentication
   • Development of Kerberos at MIT (1988)

3. 1990s:

   • World Wide Web emerges
   • HTTP Basic Authentication introduced
   • SSL/TLS for encrypted connections
   • LDAP (Lightweight Directory Access Protocol) standardized

4. 2000s:

   • Single Sign-On (SSO) concepts gain traction
   • SAML (Security Assertion Markup Language) introduced (2002)
   • OpenID first released (2005)
   • OAuth 1.0 specification published (2007)

5. 2010s:

   • OAuth 2.0 released (2012)
   • Two-Factor Authentication (2FA) becomes more common
   • OpenID Connect built on top of OAuth 2.0 (2014)
   • Increasing use of biometric authentication (fingerprint, face recognition)

6. 2020s:

   • Passwordless authentication gains popularity
   • Continued focus on multi-factor authentication (MFA)
   • Adoption of WebAuthn standard for web authentication