Negotiate authentication

Negotiate authentication is a wrapper of GSSAPI, which in turn is a wrapper over Kerberos or NTLM authentication schemes. This protocol is used in Microsoft Active Directory enabled environments with modern versions of the Microsoft Internet Explorer, Mozilla Firefox, and Google Chrome browsers. In this protocol, the credentials are exchanged with the Squid proxy server using the Kerberos mechanism. This authentication scheme is more secure compared to NTLM authentication and is preferred over NTLM.