I assume that means Kerberos, as opposed to GSSAPI mechanisms like (the moribund?) ABFAB, (now rightly deprecated?) Globus GSI, or even NTLM. I've used Kerbero

I assume that means Kerberos, as opposed to GSSAPI mechanisms like (the moribund?) ABFAB, (now rightly deprecated?) Globus GSI, or even NTLM. I've used Kerberos GSSAPI with ssh long ago, but no longer can at work. Incidentally, people arguing for X.509 might consider why GSI is such a dirty word in the research computing circles I know! I think it's still widely used in HEP, and even the US Access system, though.