The Cisco WSA supports mainly two authentication protocols: LDAP and NTLM. LDAP is a standard protocol for accessing directory services, such as Active Directory or OpenLDAP. NTLM is a proprietary protocol for authenticating Windows clients to Windows servers. NTLM has two versions: NTLMv1 and NTLMv2. NTLMSSP (NT LAN Manager Security Support Provider) is a variant of NTLMv2 that provides additional security features, such as message integrity and confidentiality. The Cisco WSA supports both LDAP and NTLMSSP using basic authentication, which requires the user to enter a username and password.
The Cisco WSA also supports Kerberos, which is a network authentication protocol that uses tickets to authenticate users and services. Kerberos is based on symmetric-key cryptography and requires a trusted third party, called the Key Distribution Center (KDC), to issue and validate tickets. Kerberos is more secure and efficient than NTLM, as it does not require the user to enter credentials repeatedly and does not send passwords over the network. The Cisco WSA supports Kerberos only in standard mode, not in cloud connector mode. The Cisco WSA does not support TACACS+ or CHAP as authentication protocols.
TACACS+ is a Cisco proprietary protocol for authenticating network devices and users to a central server.
CHAP is a challenge-response protocol for authenticating PPP connections. These protocols are not designed for web security appliances and are not compatible with the Cisco WSA. References:
* User Guide for AsyncOS 11.0 for Cisco Web Security Appliances (Section: Acquire End-User Credentials)
* Cisco WSA Authentication
* WSA Authentication