Kerberos is the primary authentication protocol used in Active Directory environments. It provides secure authentication by using secret-key cryptography and a trusted third-party (Key Distribution Center) to facilitate mutual authentication between clients and services.
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A) LDAP (Lightweight Directory Access Protocol): While LDAP is used by Active Directory, it's a directory service protocol used for querying and modifying directory data, not the primary authentication protocol. It can be used with authentication mechanisms like Kerberos, but it's not the authentication protocol itself.
B) NTLM (NT LAN Manager): NTLM is an older authentication protocol used in Windows NT and earlier systems. While Active Directory may support it for backward compatibility, it's largely superseded by Kerberos due to security vulnerabilities.
D) RADIUS (Remote Authentication Dial-In User Service): RADIUS is a networking protocol that provides centralized Authentication, Authorization, and Accounting (AAA) management for users who connect and use a network service. It's commonly used for network access control (like Wi-Fi authentication) and not the core authentication protocol within an Active Directory domain.