

A person I know, belonging to a research lab of a rivate
company, claimed to me during a priavte conversation that, given the
equipment in his lab, he could crack a Kerberos ticket in 15 minutes to
an hour. He had access to rather powerful DES hardware, but not of an
extraordinare kind, I believe. The attack was possible because of the
amount of known plaintext in the ticket, which itself constitutes a small
message. This was two years ago.
DES is no longer usable for encryption of really sensitive data. For a
lot of purposes, however, it is still very adequate.