<s>
Distributed	B-Language
Access	I-Language
Control	I-Language
System	I-Language
(	O
DACS	O
)	O
is	O
a	O
light-weight	O
single	O
sign-on	O
and	O
attribute-based	O
access	O
control	O
system	O
for	O
web	B-Application
servers	I-Application
and	O
server-based	B-Application
software	I-Application
.	O
</s>
<s>
Apache	B-Application
servers	I-Application
.	O
</s>
<s>
Released	O
under	O
an	O
open-source	O
license	O
,	O
DACS	O
provides	O
a	O
modular	O
authentication	O
framework	B-Architecture
that	O
supports	O
an	O
array	O
of	O
common	O
authentication	O
methods	O
and	O
a	O
rule-based	O
authorization	O
engine	O
that	O
can	O
grant	O
or	O
deny	O
access	O
to	O
resources	O
,	O
named	O
by	O
URLs	O
,	O
based	O
on	O
the	O
identity	O
of	O
the	O
requestor	O
and	O
other	O
contextual	O
information	O
.	O
</s>
<s>
In	O
addition	O
to	O
simple	O
web-based	O
APIs	B-Application
,	O
command-line	B-Application
interfaces	I-Application
are	O
also	O
provided	O
to	O
much	O
of	O
the	O
functionality	O
.	O
</s>
<s>
Most	O
web-based	O
APIs	B-Application
can	O
return	O
XML	B-Protocol
or	O
JSON	B-General_Concept
documents	O
.	O
</s>
<s>
such	O
as	O
message	B-Algorithm
digests	I-Algorithm
,	O
HMACs	B-Algorithm
,	O
</s>
<s>
ciphers	O
(	O
ChaCha20	O
,	O
OpenSSL	B-Language
)	O
,	O
</s>
<s>
password-based	O
key	O
derivation	O
functions	O
(	O
HKDF	B-Algorithm
,	O
PBKDF2	O
)	O
,	O
</s>
<s>
memory-hard	O
key	O
derivation	O
functions	O
(	O
scrypt	B-Algorithm
,	O
Argon2	B-Algorithm
)	O
,	O
</s>
