<s>
The	O
Central	B-Language
Authentication	I-Language
Service	I-Language
(	O
CAS	O
)	O
is	O
a	O
single	O
sign-on	O
protocol	O
for	O
the	O
web	O
.	O
</s>
<s>
The	O
name	O
CAS	O
also	O
refers	O
to	O
a	O
software	B-Application
package	I-Application
that	O
implements	O
this	O
protocol	O
.	O
</s>
<s>
CAS	O
validates	O
the	O
client	O
's	O
authenticity	O
,	O
usually	O
by	O
checking	O
a	O
username	O
and	O
password	O
against	O
a	O
database	O
(	O
such	O
as	O
Kerberos	B-Protocol
,	O
LDAP	B-Protocol
or	O
Active	B-Protocol
Directory	I-Protocol
)	O
.	O
</s>
<s>
If	O
the	O
authentication	O
succeeds	O
,	O
CAS	O
returns	O
the	O
client	O
to	O
the	O
application	O
,	O
passing	O
along	O
a	O
service	B-General_Concept
ticket	I-General_Concept
.	O
</s>
<s>
The	O
application	O
then	O
validates	O
the	O
ticket	B-General_Concept
by	O
contacting	O
CAS	O
over	O
a	O
secure	O
connection	O
and	O
providing	O
its	O
own	O
service	O
identifier	O
and	O
the	O
ticket	B-General_Concept
.	O
</s>
<s>
CAS	O
allows	O
multi-tier	O
authentication	O
via	O
proxy	B-Application
address	I-Application
.	O
</s>
<s>
Authentication	O
via	O
JAAS	B-Language
,	O
LDAP	B-Protocol
,	O
RDBMS	O
,	O
X.509	O
,	O
Radius	O
,	O
SPNEGO	B-Protocol
,	O
JWT	B-General_Concept
,	O
Remote	O
,	O
Trusted	O
,	O
BASIC	O
,	O
Apache	B-Language
Shiro	I-Language
,	O
MongoDB	B-Application
,	O
Pac4J	O
and	O
more	O
.	O
</s>
<s>
HA	O
clustered	O
deployments	O
via	O
Hazelcast	B-Application
,	O
Ehcache	B-Language
,	O
JPA	O
,	O
Memcached	B-Application
,	O
Apache	B-Application
Ignite	I-Application
,	O
MongoDB	B-Application
,	O
Redis	B-Operating_System
,	O
Couchbase	O
and	O
more	O
.	O
</s>
<s>
Application	O
registration	O
backed	O
by	O
JSON	B-General_Concept
,	O
LDAP	B-Protocol
,	O
YAML	B-Protocol
,	O
JPA	O
,	O
Couchbase	O
,	O
MongoDB	B-Application
and	O
more	O
.	O
</s>
<s>
Multifactor	O
authentication	O
via	O
Duo	O
Security	O
,	O
SAASPASS	O
,	O
YubiKey	O
,	O
RSA	O
,	O
Google	O
Authenticator	O
(	O
TOTP	B-Algorithm
)	O
and	O
more	O
.	O
</s>
