@table @b
@item client
an entity that can obtain a ticket. This entity is usually either a
user or a host.
@item host
a computer that can be accessed over a network.
@item Kerberos
in Greek mythology, the three-headed dog that guards the entrance to the
underworld. In the computing world, Kerberos is a network security
package that was developed at MIT.
@item KDC
Key Distribution Center. A machine that issues Kerberos tickets.
@item keytab
a @b{key tab}le file containing one or more keys. A host or service
uses a @dfn{keytab} file in much the same way as a user uses his/her
password.
@item principal
a string that names a specific entity to which a set of credentials may
be assigned. It can have an arbitrary number of components, but
generally has three:
@table @b
@item primary
the first part of a Kerberos @i{principal}. In the case of a user, it
is the username. In the case of a service, it is the name of the
service.
@item instance
the second part of a Kerberos @i{principal}. It gives information that
qualifies the primary. The instance may be null. In the case of a
user, the instance is often used to describe the intended use of the
corresponding credentials. In the case of a host, the instance is the
fully qualified hostname.
@item realm
the logical network served by a single Kerberos database and a set of
Key Distribution Centers. By convention, realm names are generally all
uppercase letters, to differentiate the realm from the internet domain.
@end table
@noindent
The typical format of a typical Kerberos principal is
primary/instance@@REALM.
@item service
any program or computer you access over a network. Examples of services
include ``host'' (a host, @i{e.g.}, when you use @code{telnet} and
@code{rsh}), ``ftp'' (FTP), ``krbtgt'' (authentication;
cf. @i{ticket-granting ticket}), and ``pop'' (email).
@item ticket
a temporary set of electronic credentials that verify the identity of a
client for a particular service.
@item TGT
Ticket-Granting Ticket. A special Kerberos ticket that permits the
client to obtain additional Kerberos tickets within the same Kerberos
realm.
@end table