<s>
The	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
Security	I-Protocol
Extensions	I-Protocol
(	O
DNSSEC	B-Protocol
)	O
are	O
a	O
suite	O
of	O
extension	O
specifications	O
by	O
the	O
Internet	O
Engineering	O
Task	O
Force	O
(	O
IETF	O
)	O
for	O
securing	O
data	O
exchanged	O
in	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Application
)	O
in	O
Internet	B-Protocol
Protocol	I-Protocol
(	O
IP	O
)	O
networks	O
.	O
</s>
<s>
The	O
protocol	O
provides	O
cryptographic	B-Error_Name
authentication	I-Error_Name
of	O
data	O
,	O
authenticated	O
denial	O
of	O
existence	O
,	O
and	O
data	O
integrity	O
,	O
but	O
not	O
availability	O
or	O
confidentiality	O
.	O
</s>
<s>
The	O
original	O
design	O
of	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
did	O
not	O
include	O
any	O
security	O
features	O
.	O
</s>
<s>
The	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
Security	I-Protocol
Extensions	I-Protocol
(	O
DNSSEC	B-Protocol
)	O
attempt	O
to	O
add	O
security	O
,	O
while	O
maintaining	O
backward	B-General_Concept
compatibility	I-General_Concept
.	O
</s>
<s>
Request	O
for	O
Comments	O
3833	O
documents	O
some	O
of	O
the	O
known	O
threats	O
to	O
the	O
DNS	B-Application
,	O
and	O
their	O
solutions	O
in	O
DNSSEC	B-Protocol
.	O
</s>
<s>
DNSSEC	B-Protocol
was	O
designed	O
to	O
protect	O
applications	O
using	O
DNS	B-Application
from	O
accepting	O
forged	O
or	O
manipulated	O
DNS	B-Application
data	O
,	O
such	O
as	O
that	O
created	O
by	O
DNS	B-Application
cache	O
poisoning	O
.	O
</s>
<s>
All	O
answers	O
from	O
DNSSEC	B-Protocol
protected	O
zones	O
are	O
digitally	O
signed	O
.	O
</s>
<s>
By	O
checking	O
the	O
digital	O
signature	O
,	O
a	O
DNS	B-Application
resolver	O
is	O
able	O
to	O
check	O
if	O
the	O
information	O
is	O
identical	O
(	O
i.e.	O
</s>
<s>
unmodified	O
and	O
complete	O
)	O
to	O
the	O
information	O
published	O
by	O
the	O
zone	O
owner	O
and	O
served	O
on	O
an	O
authoritative	O
DNS	B-Application
server	O
.	O
</s>
<s>
While	O
protecting	O
IP	O
addresses	O
is	O
the	O
immediate	O
concern	O
for	O
many	O
users	O
,	O
DNSSEC	B-Protocol
can	O
protect	O
any	O
data	O
published	O
in	O
the	O
DNS	B-Application
,	O
including	O
text	O
records	O
(	O
TXT	O
)	O
and	O
mail	O
exchange	O
records	O
(	O
MX	O
)	O
,	O
and	O
can	O
be	O
used	O
to	O
bootstrap	O
other	O
security	O
systems	O
that	O
publish	O
references	O
to	O
cryptographic	O
certificates	O
stored	O
in	O
the	O
DNS	B-Application
such	O
as	O
Certificate	O
Records	O
(	O
CERT	O
records	O
,	O
RFC	O
4398	O
)	O
,	O
SSH	B-Protocol
fingerprints	O
(	O
SSHFP	B-Protocol
,	O
RFC	O
4255	O
)	O
,	O
IPSec	B-Protocol
public	B-Application
keys	I-Application
(	O
IPSECKEY	O
,	O
RFC	O
4025	O
)	O
,	O
TLS	B-Protocol
Trust	B-General_Concept
Anchors	I-General_Concept
(	O
TLSA	B-Protocol
,	O
RFC	O
6698	O
)	O
,	O
or	O
Encrypted	O
Client	O
Hello	O
(	O
SVCB/HTTPS	O
records	O
for	O
ECH	O
,	O
)	O
.	O
</s>
<s>
DNSSEC	B-Protocol
does	O
not	O
provide	O
confidentiality	O
of	O
data	O
;	O
in	O
particular	O
,	O
all	O
DNSSEC	B-Protocol
responses	O
are	O
authenticated	O
but	O
not	O
encrypted	O
.	O
</s>
<s>
DNSSEC	B-Protocol
does	O
not	O
protect	O
against	O
DoS	O
attacks	O
directly	O
,	O
though	O
it	O
indirectly	O
provides	O
some	O
benefit	O
(	O
because	O
signature	O
checking	O
allows	O
the	O
use	O
of	O
potentially	O
untrustworthy	O
parties	O
)	O
.	O
</s>
<s>
Other	O
standards	O
(	O
not	O
DNSSEC	B-Protocol
)	O
are	O
used	O
to	O
secure	O
bulk	O
data	O
(	O
such	O
as	O
a	O
DNS	B-Protocol
zone	I-Protocol
transfer	I-Protocol
)	O
sent	O
between	O
DNS	B-Application
servers	O
.	O
</s>
<s>
As	O
documented	O
in	O
IETF	O
RFC	O
4367	O
,	O
some	O
users	O
and	O
developers	O
make	O
false	O
assumptions	O
about	O
DNS	B-Protocol
names	I-Protocol
,	O
such	O
as	O
assuming	O
that	O
a	O
company	O
's	O
common	O
name	O
plus	O
"	O
.com	O
"	O
is	O
always	O
its	O
domain	O
name	O
.	O
</s>
<s>
DNSSEC	B-Protocol
cannot	O
protect	O
against	O
false	O
assumptions	O
;	O
it	O
can	O
only	O
authenticate	O
that	O
the	O
data	O
is	O
truly	O
from	O
or	O
not	O
available	O
from	O
the	O
domain	O
owner	O
.	O
</s>
<s>
The	O
DNSSEC	B-Protocol
specifications	O
(	O
called	O
DNSSEC-bis	B-Protocol
)	O
describe	O
the	O
current	O
DNSSEC	B-Protocol
protocol	O
in	O
great	O
detail	O
.	O
</s>
<s>
It	O
is	O
widely	O
believed	O
that	O
securing	O
the	O
DNS	B-Application
is	O
critically	O
important	O
for	O
securing	O
the	O
Internet	O
as	O
a	O
whole	O
,	O
but	O
deployment	O
of	O
DNSSEC	B-Protocol
specifically	O
has	O
been	O
hampered	O
(	O
)	O
by	O
several	O
difficulties	O
:	O
</s>
<s>
DNSSEC	B-Protocol
works	O
by	O
digitally	O
signing	O
records	O
for	O
DNS	B-Application
lookup	O
using	O
public-key	B-Application
cryptography	I-Application
.	O
</s>
<s>
The	O
correct	O
DNSKEY	O
record	O
is	O
authenticated	O
via	O
a	O
chain	O
of	O
trust	O
,	O
starting	O
with	O
a	O
set	O
of	O
verified	O
public	B-Application
keys	I-Application
for	O
the	O
DNS	B-Protocol
root	I-Protocol
zone	I-Protocol
which	O
is	O
the	O
trusted	O
third	O
party	O
.	O
</s>
<s>
Domain	O
owners	O
generate	O
their	O
own	O
keys	O
,	O
and	O
upload	O
them	O
using	O
their	O
DNS	B-Application
control	O
panel	O
at	O
their	O
domain-name	O
registrar	O
,	O
which	O
in	O
turn	O
pushes	O
the	O
keys	O
via	O
secDNS	O
to	O
the	O
zone	O
operator	O
(	O
e.g.	O
,	O
Verisign	B-Application
for	O
.com	O
)	O
who	O
signs	O
and	O
publishes	O
them	O
in	O
DNS	B-Application
.	O
</s>
<s>
DNS	B-Application
is	O
implemented	O
by	O
the	O
use	O
of	O
several	O
resource	O
records	O
.	O
</s>
<s>
To	O
implement	O
DNSSEC	B-Protocol
,	O
several	O
new	O
DNS	B-Protocol
record	I-Protocol
types	I-Protocol
were	O
created	O
or	O
adapted	O
to	O
use	O
with	O
DNSSEC	B-Protocol
:	O
</s>
<s>
RRSIG	B-Protocol
(	O
resource	O
record	O
signature	O
)	O
Contains	O
the	O
DNSSEC	B-Protocol
signature	O
for	O
a	B-Protocol
record	I-Protocol
set	O
.	O
</s>
<s>
DNS	B-Application
resolvers	O
verify	O
the	O
signature	O
with	O
a	O
public	B-Application
key	I-Application
,	O
stored	O
in	O
a	O
DNSKEY	O
record	O
.	O
</s>
<s>
DNSKEY	O
Contains	O
the	O
public	B-Application
key	I-Application
that	O
a	O
DNS	B-Application
resolver	O
uses	O
to	O
verify	O
DNSSEC	B-Protocol
signatures	O
in	O
RRSIG	B-Protocol
records	O
.	O
</s>
<s>
DNS	B-Application
resolvers	O
use	O
NSEC	O
records	O
to	O
verify	O
the	O
non-existence	O
of	O
a	B-Protocol
record	I-Protocol
name	O
and	O
type	O
as	O
part	O
of	O
DNSSEC	B-Protocol
validation	O
.	O
</s>
<s>
NSEC3	O
(	O
next	O
secure	O
record	O
version	O
3	O
)	O
Contains	O
links	O
to	O
the	O
next	O
record	O
name	O
in	O
the	O
zone	O
(	O
in	O
hashed	O
name	O
sorting	O
order	O
)	O
and	O
lists	O
the	O
record	O
types	O
that	O
exist	O
for	O
the	O
name	O
covered	O
by	O
the	O
hash	B-Algorithm
value	O
in	O
the	O
first	O
label	O
of	O
the	O
NSEC3	O
record	O
's	O
own	O
name	O
.	O
</s>
<s>
These	O
records	O
can	O
be	O
used	O
by	O
resolvers	O
to	O
verify	O
the	O
non-existence	O
of	O
a	B-Protocol
record	I-Protocol
name	O
and	O
type	O
as	O
part	O
of	O
DNSSEC	B-Protocol
validation	O
.	O
</s>
<s>
NSEC3PARAM	O
(	O
next	O
secure	O
record	O
version	O
3	O
parameters	O
)	O
Authoritative	O
DNS	B-Application
servers	O
use	O
this	O
record	O
to	O
calculate	O
and	O
determine	O
which	O
NSEC3	O
records	O
to	O
include	O
in	O
responses	O
to	O
DNSSEC	B-Protocol
requests	O
for	O
non-existing	O
names/types	O
.	O
</s>
<s>
When	O
DNSSEC	B-Protocol
is	O
used	O
,	O
each	O
answer	O
to	O
a	O
DNS	B-Application
lookup	O
contains	O
an	O
RRSIG	B-Protocol
DNS	B-Application
record	O
,	O
in	O
addition	O
to	O
the	O
record	O
type	O
that	O
was	O
requested	O
.	O
</s>
<s>
The	O
RRSIG	B-Protocol
record	O
is	O
a	O
digital	O
signature	O
of	O
the	O
answer	O
DNS	B-Application
resource	O
record	O
set	O
.	O
</s>
<s>
The	O
digital	O
signature	O
is	O
verified	O
by	O
locating	O
the	O
correct	O
public	B-Application
key	I-Application
found	O
in	O
a	O
DNSKEY	O
record	O
.	O
</s>
<s>
DNSSEC	B-Protocol
was	O
designed	O
to	O
be	O
extensible	O
so	O
that	O
as	O
attacks	O
are	O
discovered	O
against	O
existing	O
algorithms	O
,	O
new	O
ones	O
can	O
be	O
introduced	O
in	O
a	O
backward-compatible	B-General_Concept
fashion	O
.	O
</s>
<s>
From	O
the	O
results	O
of	O
a	O
DNS	B-Application
lookup	O
,	O
a	O
security-aware	O
DNS	B-Application
resolver	O
can	O
determine	O
whether	O
the	O
authoritative	O
name	O
server	O
for	O
the	O
domain	O
being	O
queried	O
supports	O
DNSSEC	B-Protocol
,	O
whether	O
the	O
answer	O
it	O
receives	O
is	O
secure	O
,	O
and	O
whether	O
there	O
is	O
some	O
sort	O
of	O
error	O
.	O
</s>
<s>
The	O
lookup	O
procedure	O
is	O
different	O
for	O
recursive	O
name	O
servers	O
such	O
as	O
those	O
of	O
many	O
ISPs	O
,	O
and	O
for	O
stub	O
resolvers	O
such	O
as	O
those	O
included	O
by	O
default	O
in	O
mainstream	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Microsoft	B-Application
Windows	I-Application
uses	O
a	O
stub	O
resolver	O
,	O
and	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
and	O
Windows	B-Device
7	I-Device
in	O
particular	O
use	O
a	O
non-validating	O
but	O
DNSSEC-aware	O
stub	O
resolver	O
.	O
</s>
<s>
Using	O
the	O
chain	O
of	O
trust	O
model	O
,	O
a	O
Delegation	O
Signer	O
(	O
DS	O
)	O
record	O
in	O
a	O
parent	O
domain	O
(	O
DNS	B-Protocol
zone	I-Protocol
)	O
can	O
be	O
used	O
to	O
verify	O
a	O
DNSKEY	O
record	O
in	O
a	O
subdomain	B-Protocol
,	O
which	O
can	O
then	O
contain	O
other	O
DS	O
records	O
to	O
verify	O
further	O
subdomains	B-Protocol
.	O
</s>
<s>
Say	O
that	O
a	O
recursive	O
resolver	O
such	O
as	O
an	O
ISP	O
name	O
server	O
wants	O
to	O
get	O
the	O
IP	O
addresses	O
(	O
A	B-Protocol
record	I-Protocol
and/or	O
AAAA	B-Protocol
records	I-Protocol
)	O
of	O
the	O
domain	O
"	O
www.example.com	O
"	O
.	O
</s>
<s>
The	O
process	O
starts	O
when	O
a	O
security-aware	O
resolver	O
sets	O
the	O
"	O
DO	O
"	O
(	O
"	O
DNSSEC	B-Protocol
OK	O
"	O
)	O
flag	O
bit	O
in	O
a	O
DNS	B-Protocol
query	I-Protocol
.	O
</s>
<s>
Since	O
the	O
DO	O
bit	O
is	O
in	O
the	O
extended	O
flag	O
bits	O
defined	O
by	O
Extension	B-Protocol
Mechanisms	I-Protocol
for	I-Protocol
DNS	I-Protocol
(	O
EDNS	B-Protocol
)	O
,	O
all	O
DNSSEC	B-Protocol
transactions	O
must	O
support	O
EDNS	B-Protocol
.	O
</s>
<s>
EDNS	B-Protocol
support	O
is	O
also	O
needed	O
to	O
allow	O
for	O
the	O
much	O
larger	O
packet	O
sizes	O
that	O
DNSSEC	B-Protocol
transactions	O
require	O
.	O
</s>
<s>
When	O
the	O
resolver	O
receives	O
an	O
answer	O
via	O
the	O
normal	O
DNS	B-Application
lookup	O
process	O
,	O
it	O
then	O
checks	O
to	O
make	O
sure	O
that	O
the	O
answer	O
is	O
correct	O
.	O
</s>
<s>
Ideally	O
,	O
the	O
security-aware	O
resolver	O
would	O
start	O
with	O
verifying	O
the	O
DS	O
and	O
DNSKEY	O
records	O
at	O
the	O
DNS	B-Protocol
root	I-Protocol
.	O
</s>
<s>
From	O
there	O
,	O
it	O
would	O
see	O
if	O
there	O
is	O
a	O
DS	O
record	O
for	O
the	O
"	O
example.com	O
 "	O
subdomain	B-Protocol
in	O
the	O
"	O
com	O
"	O
zone	O
,	O
and	O
if	O
there	O
were	O
,	O
it	O
would	O
then	O
use	O
the	O
DS	O
record	O
to	O
verify	O
a	O
DNSKEY	O
record	O
found	O
in	O
the	O
"	O
example.com	O
 "	O
zone	O
.	O
</s>
<s>
Finally	O
,	O
it	O
would	O
verify	O
the	O
RRSIG	B-Protocol
record	O
found	O
in	O
the	O
answer	O
for	O
the	O
A	B-Protocol
records	I-Protocol
for	O
"	O
www.example.com	O
"	O
.	O
</s>
<s>
First	O
,	O
if	O
"	O
example.com	O
 "	O
does	O
not	O
support	O
DNSSEC	B-Protocol
,	O
there	O
will	O
be	O
no	O
RRSIG	B-Protocol
record	O
in	O
the	O
answer	O
and	O
there	O
will	O
not	O
be	O
a	O
DS	O
record	O
for	O
"	O
example.com	O
 "	O
in	O
the	O
"	O
com	O
"	O
zone	O
.	O
</s>
<s>
If	O
there	O
is	O
a	O
DS	O
record	O
for	O
"	O
example.com	O
 "	O
,	O
but	O
no	O
RRSIG	B-Protocol
record	O
in	O
the	O
reply	O
,	O
something	O
is	O
wrong	O
and	O
maybe	O
a	O
man	O
in	O
the	O
middle	O
attack	O
is	O
going	O
on	O
,	O
stripping	O
the	O
DNSSEC	B-Protocol
information	O
and	O
modifying	O
the	O
A	B-Protocol
records	I-Protocol
.	O
</s>
<s>
Or	O
,	O
it	O
could	O
be	O
a	O
broken	O
security-oblivious	O
name	O
server	O
along	O
the	O
way	O
that	O
stripped	O
the	O
DO	O
flag	O
bit	O
from	O
the	O
query	O
or	O
the	O
RRSIG	B-Protocol
record	O
from	O
the	O
answer	O
.	O
</s>
<s>
Next	O
,	O
it	O
may	O
be	O
that	O
there	O
is	O
not	O
a	O
domain	O
name	O
named	O
"	O
www.example.com	O
"	O
,	O
in	O
which	O
case	O
instead	O
of	O
returning	O
a	O
RRSIG	B-Protocol
record	O
in	O
the	O
answer	O
,	O
there	O
will	O
be	O
either	O
an	O
NSEC	O
record	O
or	O
an	O
NSEC3	O
record	O
.	O
</s>
<s>
The	O
NSEC/NSEC3	O
records	O
have	O
RRSIG	B-Protocol
records	O
,	O
which	O
can	O
be	O
verified	O
as	O
above	O
.	O
</s>
<s>
Finally	O
,	O
it	O
may	O
be	O
that	O
the	O
"	O
example.com	O
 "	O
zone	O
implements	O
DNSSEC	B-Protocol
,	O
but	O
either	O
the	O
"	O
com	O
"	O
zone	O
or	O
the	O
root	O
zone	O
do	O
not	O
,	O
creating	O
an	O
"	O
island	O
of	O
security	O
"	O
which	O
needs	O
to	O
be	O
validated	O
in	O
some	O
other	O
way	O
.	O
</s>
<s>
,	O
deployment	O
of	O
DNSSEC	B-Protocol
to	O
root	O
is	O
completed	O
.	O
</s>
<s>
Stub	O
resolvers	O
are	O
"	O
minimal	O
DNS	B-Application
resolvers	O
that	O
use	O
recursive	O
query	O
mode	O
to	O
offload	O
most	O
of	O
the	O
work	O
of	O
DNS	B-Application
resolution	O
to	O
a	O
recursive	O
name	O
server.	O
"	O
</s>
<s>
Microsoft	B-Application
Windows	I-Application
uses	O
a	O
stub	O
resolver	O
,	O
and	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
and	O
Windows	B-Device
7	I-Device
in	O
particular	O
use	O
a	O
non-validating	O
but	O
AD-bit-aware	O
stub	O
resolver	O
.	O
</s>
<s>
Using	O
such	O
a	O
validating	O
stub	O
resolver	O
gives	O
the	O
client	O
end-to-end	O
DNS	B-Application
security	O
for	O
domains	O
implementing	O
DNSSEC	B-Protocol
,	O
even	O
if	O
the	O
Internet	O
service	O
provider	O
or	O
the	O
connection	O
to	O
them	O
is	O
not	O
trusted	O
.	O
</s>
<s>
Non-validating	O
stub	O
resolvers	O
must	O
rely	O
on	O
external	O
DNSSEC	B-Protocol
validation	O
services	O
,	O
such	O
as	O
those	O
controlled	O
by	O
the	O
user	O
's	O
Internet	O
service	O
provider	O
or	O
a	O
public	B-Operating_System
recursive	I-Operating_System
name	I-Operating_System
server	I-Operating_System
,	O
and	O
the	O
communication	O
channels	O
between	O
itself	O
and	O
those	O
name	O
servers	O
,	O
using	O
methods	O
such	O
as	O
DNS	B-Protocol
over	I-Protocol
TLS	I-Protocol
.	O
</s>
<s>
To	O
be	O
able	O
to	O
prove	O
that	O
a	O
DNS	B-Application
answer	O
is	O
correct	O
,	O
one	O
needs	O
to	O
know	O
at	O
least	O
one	O
key	O
or	O
DS	O
record	O
that	O
is	O
correct	O
from	O
sources	O
other	O
than	O
the	O
DNS	B-Application
.	O
</s>
<s>
These	O
starting	O
points	O
are	O
known	O
as	O
trust	B-General_Concept
anchors	I-General_Concept
and	O
are	O
typically	O
obtained	O
with	O
the	O
operating	B-General_Concept
system	I-General_Concept
or	O
via	O
some	O
other	O
trusted	O
source	O
.	O
</s>
<s>
When	O
DNSSEC	B-Protocol
was	O
originally	O
designed	O
,	O
it	O
was	O
thought	O
that	O
the	O
only	O
trust	B-General_Concept
anchor	I-General_Concept
that	O
would	O
be	O
needed	O
was	O
for	O
the	O
DNS	B-Protocol
root	I-Protocol
.	O
</s>
<s>
An	O
authentication	O
chain	O
is	O
a	O
series	O
of	O
linked	O
DS	O
and	O
DNSKEY	O
records	O
,	O
starting	O
with	O
a	O
trust	B-General_Concept
anchor	I-General_Concept
to	O
the	O
authoritative	O
name	O
server	O
for	O
the	O
domain	O
in	O
question	O
.	O
</s>
<s>
Without	O
a	O
complete	O
authentication	O
chain	O
,	O
an	O
answer	O
to	O
a	O
DNS	B-Application
lookup	O
cannot	O
be	O
securely	O
authenticated	O
.	O
</s>
<s>
To	O
limit	O
replay	O
attacks	O
,	O
there	O
are	O
not	O
only	O
the	O
normal	O
DNS	B-Application
TTL	O
values	O
for	O
caching	O
purposes	O
,	O
but	O
additional	O
timestamps	O
in	O
RRSIG	B-Protocol
records	O
to	O
limit	O
the	O
validity	O
of	O
a	O
signature	O
.	O
</s>
<s>
This	O
means	O
that	O
all	O
security-aware	O
DNS	B-Application
resolvers	O
must	O
have	O
clocks	O
that	O
are	O
fairly	O
closely	O
in	O
sync	O
,	O
say	O
to	O
within	O
a	O
few	O
minutes	O
.	O
</s>
<s>
DNSSEC	B-Protocol
involves	O
many	O
different	O
keys	O
,	O
stored	O
both	O
in	O
DNSKEY	O
records	O
,	O
and	O
from	O
other	O
sources	O
to	O
form	O
trust	B-General_Concept
anchors	I-General_Concept
.	O
</s>
<s>
Then	O
,	O
when	O
it	O
is	O
safe	O
to	O
assume	O
that	O
the	O
time	B-Protocol
to	I-Protocol
live	I-Protocol
values	O
have	O
caused	O
the	O
caching	O
of	O
old	O
keys	O
to	O
have	O
passed	O
,	O
these	O
new	O
keys	O
can	O
be	O
used	O
.	O
</s>
<s>
This	O
process	O
is	O
more	O
complicated	O
for	O
things	O
such	O
as	O
the	O
keys	O
to	O
trust	B-General_Concept
anchors	I-General_Concept
,	O
such	O
as	O
at	O
the	O
root	O
,	O
which	O
may	O
require	O
an	O
update	O
of	O
the	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
First	O
,	O
there	O
are	O
key	O
signing	O
keys	O
(	O
KSK	O
)	O
which	O
are	O
used	O
to	O
sign	O
other	O
DNSKEY	O
records	O
containing	O
zone	B-Protocol
signing	I-Protocol
keys	I-Protocol
(	O
ZSK	O
)	O
,	O
which	O
are	O
used	O
to	O
sign	O
other	O
records	O
.	O
</s>
<s>
Since	O
the	O
ZSKs	O
are	O
under	O
complete	O
control	O
and	O
use	O
by	O
one	O
particular	O
DNS	B-Protocol
zone	I-Protocol
,	O
they	O
can	O
be	O
switched	O
more	O
easily	O
and	O
more	O
often	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
ZSKs	O
can	O
be	O
much	O
shorter	O
than	O
KSKs	O
and	O
still	O
offer	O
the	O
same	O
level	O
of	O
protection	O
while	O
reducing	O
the	O
size	O
of	O
the	O
RRSIG/DNSKEY	O
records	O
.	O
</s>
<s>
The	O
DS	O
records	O
use	O
a	O
message	B-Algorithm
digest	I-Algorithm
of	O
the	O
KSK	O
instead	O
of	O
the	O
complete	O
key	O
in	O
order	O
to	O
keep	O
the	O
size	O
of	O
the	O
records	O
small	O
.	O
</s>
<s>
The	O
procedure	O
to	O
update	O
DS	O
keys	O
in	O
the	O
parent	O
zone	O
is	O
also	O
simpler	O
than	O
earlier	O
DNSSEC	B-Protocol
versions	O
that	O
required	O
DNSKEY	O
records	O
to	O
be	O
in	O
the	O
parent	O
zone	O
.	O
</s>
<s>
DNS-based	B-Protocol
Authentication	I-Protocol
of	I-Protocol
Named	I-Protocol
Entities	I-Protocol
(	O
DANE	O
)	O
is	O
an	O
IETF	O
working	O
group	O
with	O
the	O
goal	O
of	O
developing	O
protocols	O
and	O
techniques	O
that	O
allow	O
Internet	O
applications	O
to	O
establish	O
cryptographically	O
secured	O
communications	O
with	O
TLS	B-Protocol
,	O
DTLS	B-General_Concept
,	O
SMTP	B-Protocol
,	O
and	O
S/MIME	B-Protocol
based	O
on	O
DNSSEC	B-Protocol
.	O
</s>
<s>
The	O
new	O
protocols	O
will	O
enable	O
additional	O
assurances	O
and	O
constraints	O
for	O
the	O
traditional	O
model	O
based	O
on	O
public	B-Architecture
key	I-Architecture
infrastructure	I-Architecture
.	O
</s>
<s>
They	O
will	O
also	O
enable	O
domain	O
holders	O
to	O
assert	O
certificates	O
for	O
themselves	O
,	O
without	O
reference	O
to	O
third-party	O
certificate	B-Architecture
authorities	I-Architecture
.	O
</s>
<s>
Support	O
for	O
DNSSEC	B-Protocol
stapled	O
certificates	O
was	O
enabled	O
in	O
Google	B-Application
Chrome	I-Application
14	I-Application
,	O
but	O
was	O
later	O
removed	O
.	O
</s>
<s>
For	O
Mozilla	B-Application
Firefox	I-Application
,	O
support	O
was	O
provided	O
by	O
an	O
add-on	O
while	O
native	O
support	O
is	O
currently	O
awaiting	O
someone	O
to	O
start	O
working	O
on	O
it	O
.	O
</s>
<s>
DNS	B-Application
is	O
a	O
critical	O
and	O
fundamental	O
Internet	O
service	O
,	O
yet	O
in	O
1990	O
Steve	O
Bellovin	O
discovered	O
serious	O
security	O
flaws	O
in	O
it	O
.	O
</s>
<s>
Plans	O
were	O
made	O
to	O
deploy	O
DNSSEC	B-Protocol
based	O
on	O
RFC	O
2535	O
.	O
</s>
<s>
In	O
normal	O
operation	O
DNS	B-Application
servers	O
often	O
get	O
out	O
of	O
sync	O
with	O
their	O
parents	O
.	O
</s>
<s>
This	O
is	O
n't	O
usually	O
a	O
problem	O
,	O
but	O
when	O
DNSSEC	B-Protocol
is	O
enabled	O
,	O
this	O
out-of-sync	O
data	O
could	O
have	O
the	O
effect	O
of	O
a	O
serious	O
self-created	O
denial	O
of	O
service	O
.	O
</s>
<s>
The	O
original	O
DNSSEC	B-Protocol
required	O
a	O
complex	O
six-message	O
protocol	O
and	O
a	O
lot	O
of	O
data	O
transfers	O
to	O
perform	O
key	O
changes	O
for	O
a	O
child	O
(	O
DNS	B-Application
child	O
zones	O
had	O
to	O
send	O
all	O
of	O
their	O
data	O
up	O
to	O
the	O
parent	O
,	O
have	O
the	O
parent	O
sign	O
each	O
record	O
,	O
and	O
then	O
send	O
those	O
signatures	O
back	O
to	O
the	O
child	O
for	O
the	O
child	O
to	O
store	O
in	O
a	O
SIG	O
record	O
)	O
.	O
</s>
<s>
Also	O
,	O
public	B-Application
key	I-Application
changes	O
could	O
have	O
absurd	O
effects	O
;	O
for	O
example	O
,	O
if	O
the	O
"	O
.com	O
"	O
zone	O
changed	O
its	O
public	B-Application
key	I-Application
,	O
it	O
would	O
have	O
to	O
send	O
22	O
million	O
records	O
(	O
because	O
it	O
would	O
need	O
to	O
update	O
all	O
of	O
the	O
signatures	O
in	O
all	O
of	O
its	O
children	O
)	O
.	O
</s>
<s>
Thus	O
,	O
DNSSEC	B-Protocol
as	O
defined	O
in	O
RFC	O
2535	O
could	O
not	O
scale	O
up	O
to	O
the	O
Internet	O
.	O
</s>
<s>
The	O
IETF	O
fundamentally	O
modified	O
DNSSEC	B-Protocol
,	O
which	O
is	O
called	O
DNSSEC-bis	B-Protocol
when	O
necessary	O
to	O
distinguish	O
it	O
from	O
the	O
original	O
DNSSEC	B-Protocol
approach	O
of	O
RFC	O
2535	O
.	O
</s>
<s>
In	O
the	O
new	O
approach	O
,	O
when	O
a	O
child	O
's	O
master	O
public	B-Application
key	I-Application
changes	O
,	O
instead	O
of	O
having	O
six	O
messages	O
for	O
every	O
record	O
in	O
the	O
child	O
,	O
there	O
is	O
one	O
simple	O
message	O
:	O
the	O
child	O
sends	O
the	O
new	O
public	B-Application
key	I-Application
to	O
its	O
parent	O
(	O
signed	O
,	O
of	O
course	O
)	O
.	O
</s>
<s>
Parents	O
simply	O
store	O
one	O
master	O
public	B-Application
key	I-Application
for	O
each	O
child	O
;	O
this	O
is	O
much	O
more	O
practical	O
.	O
</s>
<s>
More	O
specifically	O
,	O
verifying	O
a	O
DNS	B-Protocol
zone	I-Protocol
's	O
KEY	O
RRset	O
requires	O
two	O
signature	O
verification	O
operations	O
instead	O
of	O
the	O
one	O
required	O
by	O
RFC	O
2535	O
(	O
there	O
is	O
no	O
impact	O
on	O
the	O
number	O
of	O
signatures	O
verified	O
for	O
other	O
types	O
of	O
RRsets	O
)	O
.	O
</s>
<s>
Most	O
view	O
this	O
as	O
a	O
small	O
price	O
to	O
pay	O
,	O
since	O
it	O
makes	O
DNSSEC	B-Protocol
deployment	O
more	O
practical	O
.	O
</s>
<s>
However	O
,	O
DNSSEC	B-Protocol
was	O
designed	O
around	O
using	O
offline	O
computers	O
to	O
sign	O
records	O
so	O
that	O
zone-signing-keys	O
could	O
be	O
kept	O
in	O
cold	O
storage	O
.	O
</s>
<s>
Thus	O
if	O
a	O
client	O
queried	O
for	O
a	B-Protocol
record	I-Protocol
at	O
the	O
non-existent	O
k.example.com,	O
the	O
server	O
would	O
respond	O
with	O
an	O
NSEC	O
record	O
stating	O
that	O
nothing	O
exists	O
between	O
a.example.com	O
and	O
z.example.com	O
.	O
</s>
<s>
The	O
NSEC3	O
records	O
(	O
RFC	O
5155	O
)	O
were	O
created	O
as	O
an	O
alternative	O
which	O
hashes	B-Algorithm
the	O
name	O
instead	O
of	O
listing	O
them	O
directly	O
.	O
</s>
<s>
has	O
been	O
proposed	O
to	O
allow	O
authoritative	O
servers	O
to	O
sign	O
NSEC	O
responses	O
without	O
having	O
to	O
keep	O
a	O
private	B-Application
key	I-Application
that	O
can	O
be	O
used	O
to	O
modify	O
the	O
zone	O
.	O
</s>
<s>
Due	O
to	O
the	O
messy	O
evolution	O
of	O
the	O
protocol	O
and	O
a	O
desire	O
to	O
preserve	O
backwards	B-General_Concept
compatibility	I-General_Concept
,	O
online	O
DNSSEC	B-Protocol
signing	O
servers	O
return	O
a	O
"	O
white	O
lie	O
"	O
instead	O
of	O
authenticating	O
a	O
denial	O
of	O
existence	O
directly	O
.	O
</s>
<s>
The	O
first	O
is	O
a	O
variation	O
on	O
the	O
"	O
white	O
lies	O
"	O
approach	O
,	O
called	O
"	O
black	O
lies	O
"	O
,	O
which	O
exploits	O
common	O
DNS	B-Application
client	O
behavior	O
to	O
state	O
the	O
nonexistence	O
more	O
compactly	O
.	O
</s>
<s>
The	O
second	O
approach	O
instead	O
chooses	O
to	O
prove	O
that	O
"	O
the	O
record	O
exists	O
but	O
the	O
requested	O
record	O
type	O
does	O
not	O
"	O
,	O
which	O
they	O
call	O
"	O
DNS	B-Application
shotgun	O
"	O
.	O
</s>
<s>
The	O
Internet	O
is	O
critical	O
infrastructure	O
,	O
yet	O
its	O
operation	O
depends	O
on	O
the	O
fundamentally	O
insecure	O
DNS	B-Application
.	O
</s>
<s>
Thus	O
,	O
there	O
is	O
strong	O
incentive	O
to	O
secure	B-Protocol
DNS	I-Protocol
,	O
and	O
deploying	O
DNSSEC	B-Protocol
is	O
generally	O
considered	O
to	O
be	O
a	O
critical	O
part	O
of	O
that	O
effort	O
.	O
</s>
<s>
For	O
example	O
,	O
the	O
U.S.	O
National	O
Strategy	O
to	O
Secure	O
Cyberspace	O
specifically	O
identified	O
the	O
need	O
to	O
secure	B-Protocol
DNS	I-Protocol
.	O
</s>
<s>
Wide-scale	O
deployment	O
of	O
DNSSEC	B-Protocol
could	O
resolve	O
many	O
other	O
security	O
problems	O
as	O
well	O
,	O
such	O
as	O
secure	O
key	O
distribution	O
for	O
e-mail	O
addresses	O
.	O
</s>
<s>
DNSSEC	B-Protocol
deployment	O
in	O
large-scale	O
networks	O
is	O
also	O
challenging	O
.	O
</s>
<s>
Ozment	O
and	O
Schechter	O
observe	O
that	O
DNSSEC	B-Protocol
(	O
and	O
other	O
technologies	O
)	O
has	O
a	O
"	O
bootstrap	O
problem	O
"	O
:	O
users	O
typically	O
only	O
deploy	O
a	O
technology	O
if	O
they	O
receive	O
an	O
immediate	O
benefit	O
,	O
but	O
if	O
a	O
minimal	O
level	O
of	O
deployment	O
is	O
required	O
before	O
any	O
users	O
receive	O
a	O
benefit	O
greater	O
than	O
their	O
costs	O
(	O
as	O
is	O
true	O
for	O
DNSSEC	B-Protocol
)	O
,	O
it	O
is	O
difficult	O
to	O
deploy	O
.	O
</s>
<s>
DNSSEC	B-Protocol
can	O
be	O
deployed	O
at	O
any	O
level	O
of	O
a	O
DNS	B-Application
hierarchy	O
,	O
but	O
it	O
must	O
be	O
widely	O
available	O
in	O
a	O
zone	O
before	O
many	O
others	O
will	O
want	O
to	O
adopt	O
it	O
.	O
</s>
<s>
DNS	B-Application
servers	O
must	O
be	O
updated	O
with	O
software	O
that	O
supports	O
DNSSEC	B-Protocol
,	O
and	O
DNSSEC	B-Protocol
data	O
must	O
be	O
created	O
and	O
added	O
to	O
the	O
DNS	B-Protocol
zone	I-Protocol
data	O
.	O
</s>
<s>
A	O
TCP/IP	O
-using	O
client	O
must	O
have	O
their	O
DNS	B-Application
resolver	O
(	O
client	O
)	O
updated	O
before	O
it	O
can	O
use	O
DNSSEC	B-Protocol
's	O
capabilities	O
.	O
</s>
<s>
What	O
is	O
more	O
,	O
any	O
resolver	O
must	O
have	O
,	O
or	O
have	O
a	O
way	O
to	O
acquire	O
,	O
at	O
least	O
one	O
public	B-Application
key	I-Application
that	O
it	O
can	O
trust	O
before	O
it	O
can	O
start	O
using	O
DNSSEC	B-Protocol
.	O
</s>
<s>
DNSSEC	B-Protocol
implementation	O
can	O
add	O
significant	O
load	O
to	O
some	O
DNS	B-Application
servers	O
.	O
</s>
<s>
Common	O
DNSSEC-signed	O
responses	O
are	O
far	O
larger	O
than	O
the	O
default	O
UDP	O
size	O
of	O
512	O
bytes	O
.	O
</s>
<s>
Yet	O
many	O
current	O
TCP	O
implementations	O
store	O
a	O
great	O
deal	O
of	O
data	O
for	O
each	O
TCP	O
connection	O
;	O
heavily	O
loaded	O
servers	O
can	O
run	O
out	O
of	O
resources	O
simply	O
trying	O
to	O
respond	O
to	O
a	O
larger	O
number	O
of	O
(	O
possibly	O
bogus	O
)	O
DNSSEC	B-Protocol
requests	O
.	O
</s>
<s>
Some	O
protocol	O
extensions	O
,	O
such	O
as	O
TCP	B-Protocol
Cookie	I-Protocol
Transactions	I-Protocol
,	O
have	O
been	O
developed	O
to	O
reduce	O
this	O
loading	O
.	O
</s>
<s>
To	O
address	O
these	O
challenges	O
,	O
significant	O
effort	O
is	O
ongoing	O
to	O
deploy	O
DNSSEC	B-Protocol
,	O
because	O
the	O
Internet	O
is	O
so	O
vital	O
to	O
so	O
many	O
organizations	O
.	O
</s>
<s>
Early	O
adopters	O
include	O
Brazil	O
(	O
.br	O
)	O
,	O
Bulgaria	O
(	O
.bg	B-General_Concept
)	O
,	O
Czech	O
Republic	O
(	O
.cz	B-General_Concept
)	O
,	O
Namibia	O
(	O
.na	O
)	O
Puerto	O
Rico	O
(	O
.pr	O
)	O
and	O
Sweden	O
(	O
.se	B-General_Concept
)	O
,	O
who	O
use	O
DNSSEC	B-Protocol
for	O
their	O
country	B-Application
code	I-Application
top-level	I-Application
domains	I-Application
;	O
RIPE	O
NCC	O
,	O
who	O
have	O
signed	O
all	O
the	O
reverse	O
lookup	O
records	O
(	O
in-addr.arpa	O
)	O
that	O
are	O
delegated	O
to	O
it	O
from	O
the	O
Internet	O
Assigned	O
Numbers	O
Authority	O
(	O
IANA	O
)	O
.	O
</s>
<s>
During	O
this	O
period	O
prior	O
to	O
the	O
production	O
signing	O
of	O
the	O
root	O
,	O
there	O
were	O
also	O
several	O
alternative	O
trust	B-General_Concept
anchors	I-General_Concept
.	O
</s>
<s>
The	O
IKS	O
Jena	O
introduced	O
one	O
on	O
January	O
19	O
,	O
2006	O
,	O
the	O
Internet	O
Systems	O
Consortium	O
introduced	O
another	O
on	O
March	O
27	O
of	O
the	O
same	O
year	O
,	O
while	O
ICANN	B-Application
themselves	O
announced	O
a	O
third	O
on	O
February	O
17	O
,	O
2009	O
.	O
</s>
<s>
On	O
June	O
23	O
,	O
2010	O
,	O
13	O
registrars	O
were	O
listed	O
as	O
offering	O
DNSSEC	B-Protocol
records	O
for	O
.ORG	O
domains	O
.	O
</s>
<s>
VeriSign	B-Application
ran	O
a	O
pilot	O
project	O
to	O
allow	O
.com	O
and	O
.net	B-Application
domains	O
to	O
register	O
themselves	O
for	O
the	O
purpose	O
of	O
NSEC3	O
experimentation	O
.	O
</s>
<s>
On	O
February	O
24	O
,	O
2009	O
,	O
they	O
announced	O
that	O
they	O
would	O
deploy	O
DNSSEC	B-Protocol
across	O
all	O
their	O
top-level	O
domains	O
(	O
.com	O
,	O
.net	B-Application
,	O
etc	O
.	O
)	O
</s>
<s>
within	O
24	O
months	O
,	O
and	O
on	O
November	O
16	O
of	O
the	O
same	O
year	O
,	O
they	O
said	O
the	O
.com	O
and	O
.net	B-Application
domains	O
would	O
be	O
signed	O
by	O
the	O
first	O
quarter	O
of	O
2011	O
,	O
after	O
delays	O
caused	O
by	O
technical	O
aspects	O
of	O
the	O
implementation	O
.	O
</s>
<s>
This	O
goal	O
was	O
achieved	O
on-schedule	O
and	O
Verisign	B-Application
's	O
DNSSEC	B-Protocol
VP	O
,	O
Matt	O
Larson	O
,	O
won	O
InfoWorld	O
's	O
Technology	O
Leadership	O
Award	O
for	O
2011	O
for	O
his	O
role	O
in	O
advancing	O
DNSSEC	B-Protocol
.	O
</s>
<s>
DNSSEC	B-Protocol
was	O
first	O
deployed	O
at	O
the	O
root	O
level	O
on	O
July	O
15	O
,	O
2010	O
.	O
</s>
<s>
This	O
is	O
expected	O
to	O
greatly	O
simplify	O
the	O
deployment	O
of	O
DNSSEC	B-Protocol
resolvers	O
,	O
since	O
the	O
root	O
trust	B-General_Concept
anchor	I-General_Concept
can	O
be	O
used	O
to	O
validate	O
any	O
DNSSEC	B-Protocol
zone	O
that	O
has	O
a	O
complete	O
chain	O
of	O
trust	O
from	O
the	O
root	O
.	O
</s>
<s>
Since	O
the	O
chain	O
of	O
trust	O
must	O
be	O
traced	O
back	O
to	O
a	O
trusted	O
root	O
without	O
interruption	O
in	O
order	O
to	O
validate	O
,	O
trust	B-General_Concept
anchors	I-General_Concept
must	O
still	O
be	O
configured	O
for	O
secure	O
zones	O
if	O
any	O
of	O
the	O
zones	O
above	O
them	O
are	O
not	O
secure	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
the	O
zone	O
"	O
signed.example.org	O
 "	O
was	O
secured	O
but	O
the	O
"	O
example.org	O
 "	O
zone	O
was	O
not	O
,	O
then	O
,	O
even	O
though	O
the	O
"	O
.org	O
"	O
zone	O
and	O
the	O
root	O
are	O
signed	O
,	O
a	O
trust	B-General_Concept
anchor	I-General_Concept
has	O
to	O
be	O
deployed	O
in	O
order	O
to	O
validate	O
the	O
zone	O
.	O
</s>
<s>
Some	O
governments	O
might	O
try	O
to	O
ban	O
DNSSEC-backed	O
encryption	O
key	O
distribution	O
.	O
</s>
<s>
In	O
September	O
2008	O
,	O
ICANN	B-Application
and	O
VeriSign	B-Application
each	O
published	O
implementation	O
proposals	O
and	O
in	O
October	O
,	O
the	O
National	O
Telecommunications	O
and	O
Information	O
Administration	O
(	O
NTIA	O
)	O
asked	O
the	O
public	O
for	O
comments	O
.	O
</s>
<s>
On	O
June	O
3	O
,	O
2009	O
,	O
the	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
(	O
NIST	O
)	O
announced	O
plans	O
to	O
sign	O
the	O
root	O
by	O
the	O
end	O
of	O
2009	O
,	O
in	O
conjunction	O
with	O
ICANN	B-Application
,	O
VeriSign	B-Application
and	O
the	O
NTIA	O
.	O
</s>
<s>
On	O
October	O
6	O
,	O
2009	O
,	O
at	O
the	O
59th	O
RIPE	O
Conference	O
meeting	O
,	O
ICANN	B-Application
and	O
VeriSign	B-Application
announced	O
the	O
planned	O
deployment	O
timeline	O
for	O
deploying	O
DNSSEC	B-Protocol
within	O
the	O
root	O
zone	O
.	O
</s>
<s>
At	O
the	O
meeting	O
it	O
was	O
announced	O
that	O
it	O
would	O
be	O
incrementally	O
deployed	O
to	O
one	O
root	O
name	O
server	O
a	O
month	O
,	O
starting	O
on	O
December	O
1	O
,	O
2009	O
,	O
with	O
the	O
final	O
root	O
name	O
server	O
serving	O
a	O
DNSSEC	B-Protocol
signed	O
zone	O
on	O
July	O
1	O
,	O
2010	O
,	O
and	O
the	O
root	O
zone	O
will	O
be	O
signed	O
with	O
a	O
RSA/SHA256	O
DNSKEY	O
.	O
</s>
<s>
This	O
means	O
the	O
keys	O
that	O
were	O
used	O
to	O
sign	O
the	O
zone	O
use	O
are	O
deliberately	O
unverifiable	O
;	O
the	O
reason	O
for	O
this	O
deployment	O
was	O
to	O
monitor	O
changes	O
in	O
traffic	O
patterns	O
caused	O
by	O
the	O
larger	O
responses	O
to	O
queries	O
requesting	O
DNSSEC	B-Protocol
resource	O
records	O
.	O
</s>
<s>
The	O
.org	O
top-level	O
domain	O
has	O
been	O
signed	O
with	O
DNSSEC	B-Protocol
in	O
June	O
2010	O
,	O
followed	O
by	O
.com	O
,	O
.net	B-Application
,	O
and	O
.edu	O
later	O
in	O
2010	O
and	O
2011	O
.	O
</s>
<s>
Country	B-Application
code	I-Application
top-level	I-Application
domains	I-Application
were	O
able	O
to	O
deposit	O
keys	O
starting	O
in	O
May	O
2010	O
.	O
more	O
than	O
25%	O
of	O
top-level	O
domains	O
are	O
signed	O
with	O
DNSSEC	B-Protocol
.	O
</s>
<s>
The	O
zone	O
uses	O
signatures	O
of	O
a	O
SHA-2	B-Algorithm
(	O
SHA-256	B-Algorithm
)	O
hash	B-Algorithm
created	O
using	O
the	O
RSA	B-Architecture
algorithm	I-Architecture
,	O
as	O
defined	O
in	O
RFC	O
5702	O
.	O
</s>
<s>
On	O
July	O
15	O
,	O
2010	O
,	O
the	O
first	O
root	O
full	O
production	O
DNSSEC	B-Protocol
root	O
zone	O
was	O
signed	O
,	O
with	O
the	O
SOA	O
serial	O
2010071501	O
.	O
</s>
<s>
Root	O
trust	B-General_Concept
anchors	I-General_Concept
are	O
.	O
</s>
<s>
Underneath	O
the	O
root	O
there	O
is	O
a	O
large	O
set	O
of	O
top-level	O
domains	O
that	O
must	O
be	O
signed	O
in	O
order	O
to	O
achieve	O
full	O
DNSSEC	B-Protocol
deployment	O
.	O
</s>
<s>
The	O
List	B-Application
of	I-Application
Internet	I-Application
top-level	I-Application
domains	I-Application
provides	O
details	O
about	O
which	O
of	O
the	O
existing	O
top-level	O
domains	O
have	O
been	O
signed	O
and	O
linked	O
to	O
the	O
root	O
.	O
</s>
<s>
In	O
March	O
2006	O
,	O
the	O
Internet	O
Systems	O
Consortium	O
introduced	O
the	O
DNSSEC	B-Protocol
Lookaside	O
Validation	O
registry	O
.	O
</s>
<s>
DLV	O
was	O
intended	O
to	O
make	O
DNSSEC	B-Protocol
easier	O
to	O
deploy	O
in	O
the	O
absence	O
of	O
a	O
root	O
trust	B-General_Concept
anchor	I-General_Concept
.	O
</s>
<s>
At	O
the	O
time	O
it	O
was	O
imagined	O
that	O
a	O
validator	O
might	O
have	O
to	O
maintain	O
large	O
numbers	O
of	O
trust	B-General_Concept
anchors	I-General_Concept
corresponding	O
to	O
signed	O
subtrees	O
of	O
the	O
DNS	B-Application
.	O
</s>
<s>
The	O
purpose	O
of	O
DLV	O
was	O
to	O
allow	O
validators	O
to	O
offload	O
the	O
effort	O
of	O
managing	O
a	O
trust	B-General_Concept
anchor	I-General_Concept
repository	O
to	O
a	O
trusted	O
third	O
party	O
.	O
</s>
<s>
The	O
DLV	O
registry	O
maintained	O
a	O
central	O
list	O
of	O
trust	B-General_Concept
anchors	I-General_Concept
,	O
instead	O
of	O
each	O
validator	O
repeating	O
the	O
work	O
of	O
maintaining	O
its	O
own	O
list	O
.	O
</s>
<s>
To	O
use	O
DLV	O
,	O
a	O
validator	O
that	O
supports	O
it	O
was	O
needed	O
,	O
such	O
as	O
BIND	B-Protocol
or	O
Unbound	B-Protocol
,	O
configured	O
with	O
a	O
trust	B-General_Concept
anchor	I-General_Concept
for	O
a	O
DLV	O
zone	O
.	O
</s>
<s>
This	O
zone	O
contained	O
DLV	O
records	O
;	O
these	O
had	O
exactly	O
the	O
same	O
format	O
as	O
DS	O
records	O
,	O
but	O
instead	O
of	O
referring	O
to	O
a	O
delegated	O
sub-zone	O
,	O
they	O
referred	O
to	O
a	O
zone	O
elsewhere	O
in	O
the	O
DNS	B-Application
tree	O
.	O
</s>
<s>
Gaps	O
in	O
the	O
chain	O
of	O
trust	O
,	O
such	O
as	O
unsigned	O
top-level	O
domains	O
or	O
registrars	O
that	O
did	O
not	O
support	O
DNSSEC	B-Protocol
delegations	O
,	O
meant	O
administrators	O
of	O
lower-level	O
domains	O
could	O
use	O
DLV	O
to	O
allow	O
their	O
DNS	B-Application
data	O
to	O
be	O
validated	O
by	O
resolvers	O
which	O
had	O
been	O
configured	O
to	O
use	O
DLV	O
.	O
</s>
<s>
This	O
may	O
have	O
hindered	O
DNSSEC	B-Protocol
deployment	O
by	O
taking	O
pressure	O
off	O
registrars	O
and	O
TLD	O
registries	O
to	O
properly	O
support	O
DNSSEC	B-Protocol
.	O
</s>
<s>
DLV	O
also	O
added	O
complexity	O
by	O
adding	O
more	O
actors	O
and	O
code	O
paths	O
for	O
DNSSEC	B-Protocol
validation	O
.	O
</s>
<s>
Unbound	B-Protocol
version	O
1.5.4	O
(	O
July	O
2015	O
)	O
marked	O
DLV	O
as	O
decommissioned	O
in	O
the	O
example	O
configuration	O
and	O
manual	O
page	O
.	O
</s>
<s>
Knot	O
Resolver	O
and	O
PowerDNS	B-Language
Recursor	O
never	O
implemented	O
DLV	O
.	O
</s>
<s>
The	O
Science	O
and	O
Technology	O
Directorate	O
of	O
the	O
U.S.	O
Department	O
of	O
Homeland	O
Security	O
(	O
DHS	O
)	O
sponsors	O
the	O
"	O
DNSSEC	B-Protocol
Deployment	O
Initiative	O
"	O
.	O
</s>
<s>
DHS	O
also	O
funds	O
efforts	O
to	O
mature	O
DNSSEC	B-Protocol
and	O
get	O
it	O
deployed	O
inside	O
the	O
U.S.	O
federal	O
government	O
.	O
</s>
<s>
It	O
was	O
reported	O
that	O
on	O
March	O
30	O
,	O
2007	O
,	O
the	O
U.S.	O
Department	O
of	O
Homeland	O
Security	O
proposed	O
"	O
to	O
have	O
the	O
key	O
to	O
sign	O
the	O
DNS	B-Protocol
root	I-Protocol
zone	I-Protocol
solidly	O
in	O
the	O
hands	O
of	O
the	O
US	O
government.	O
"	O
</s>
<s>
DHS	O
later	O
commented	O
on	O
why	O
they	O
believe	O
others	O
jumped	O
to	O
the	O
false	O
conclusion	O
that	O
the	O
U.S.	O
Government	O
had	O
made	O
such	O
a	O
proposal	O
:	O
"	O
The	O
U.S.	O
Department	O
of	O
Homeland	O
Security	O
is	O
funding	O
the	O
development	O
of	O
a	O
technical	O
plan	O
for	O
implementing	O
DNSSec	B-Protocol
,	O
and	O
last	O
October	O
distributed	O
an	O
initial	O
draft	O
of	O
it	O
to	O
a	O
long	O
list	O
of	O
international	O
experts	O
for	O
comments	O
.	O
</s>
<s>
The	O
National	O
Institute	O
of	O
Standards	O
and	O
Technology	O
(	O
NIST	O
)	O
published	O
NIST	O
Special	O
Publication	O
800-81	O
Secure	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Application
)	O
Deployment	O
Guide	O
on	O
May	O
16	O
,	O
2006	O
,	O
with	O
guidance	O
on	O
how	O
to	O
deploy	O
DNSSEC	B-Protocol
.	O
</s>
<s>
NIST	O
intended	O
to	O
release	O
new	O
DNSSEC	B-Protocol
Federal	O
Information	O
Security	O
Management	O
Act	O
(	O
FISMA	O
)	O
requirements	O
in	O
NIST	O
SP800-53-R1	O
,	O
referencing	O
this	O
deployment	O
guide	O
.	O
</s>
<s>
On	O
22	O
August	O
2008	O
,	O
the	O
Office	O
of	O
Management	O
and	O
Budget	O
(	O
OMB	O
)	O
released	O
a	O
memorandum	O
requiring	O
U.S.	O
Federal	O
Agencies	O
to	O
deploy	O
DNSSEC	B-Protocol
across	O
.gov	O
sites	O
;	O
the	O
.gov	O
root	O
must	O
be	O
signed	O
by	O
January	O
2009	O
,	O
and	O
all	O
subdomains	B-Protocol
under	O
.gov	O
must	O
be	O
signed	O
by	O
December	O
2009	O
.	O
</s>
<s>
While	O
the	O
memo	O
focuses	O
on	O
.gov	O
sites	O
,	O
the	O
U.S.	O
Defense	O
Information	O
Systems	O
Agency	O
says	O
it	O
intends	O
to	O
meet	O
OMB	O
DNSSEC	B-Protocol
requirements	O
in	O
the	O
.mil	O
(	O
U.S.	O
military	O
)	O
domain	O
as	O
well	O
.	O
</s>
<s>
NetworkWorld	O
's	O
Carolyn	O
Duffy	O
Marsan	O
stated	O
that	O
DNSSEC	B-Protocol
"	O
has	O
n't	O
been	O
widely	O
deployed	O
because	O
it	O
suffers	O
from	O
a	O
classic	O
chicken-and-egg	O
dilemma	O
...	O
with	O
the	O
OMB	O
mandate	O
,	O
it	O
appears	O
the	O
egg	O
is	O
cracking.	O
"	O
</s>
<s>
Several	O
ISPs	O
have	O
started	O
to	O
deploy	O
DNSSEC-validating	O
DNS	B-Application
recursive	O
resolvers	O
.	O
</s>
<s>
According	O
to	O
a	O
study	O
at	O
APNIC	O
,	O
the	O
proportion	O
of	O
clients	O
who	O
exclusively	O
use	O
DNS	B-Application
resolvers	O
that	O
perform	O
DNSSEC	B-Protocol
validation	O
rose	O
to	O
8.3	O
%	O
in	O
May	O
2013	O
.	O
</s>
<s>
About	O
half	O
of	O
these	O
clients	O
were	O
using	O
Google	B-Protocol
's	I-Protocol
public	I-Protocol
DNS	I-Protocol
resolver	I-Protocol
.	O
</s>
<s>
In	O
September	O
2015	O
,	O
Verisign	B-Application
announced	O
their	O
free	O
public	B-Operating_System
DNS	I-Operating_System
resolver	I-Operating_System
service	O
,	O
and	O
although	O
unmentioned	O
in	O
their	O
press	O
releases	O
,	O
it	O
also	O
performs	O
DNSSEC	B-Protocol
validation	O
.	O
</s>
<s>
By	O
the	O
beginning	O
of	O
2016	O
,	O
APNIC	O
's	O
monitoring	O
showed	O
the	O
proportion	O
of	O
clients	O
who	O
exclusively	O
use	O
DNS	B-Application
resolvers	O
that	O
perform	O
DNSSEC	B-Protocol
validation	O
had	O
increased	O
to	O
about	O
15%	O
.	O
</s>
<s>
Google	O
's	O
public	B-Protocol
recursive	I-Protocol
DNS	I-Protocol
server	O
enabled	O
DNSSEC	B-Protocol
validation	O
on	O
May	O
6	O
,	O
2013	O
.	O
</s>
<s>
BIND	B-Protocol
,	O
the	O
most	O
popular	O
DNS	B-Protocol
management	I-Protocol
software	I-Protocol
,	O
enables	O
DNSSEC	B-Protocol
support	O
by	O
default	O
since	O
version	O
9.5	O
.	O
</s>
<s>
The	O
Quad9	B-Protocol
public	I-Protocol
recursive	I-Protocol
DNS	I-Protocol
has	O
performed	O
DNSSEC	B-Protocol
validation	O
on	O
its	O
main	O
9.9.9.9	B-Protocol
address	O
since	O
it	O
was	O
established	O
on	O
May	O
11	O
,	O
2016	O
.	O
</s>
<s>
Quad9	B-Protocol
also	O
provides	O
an	O
alternate	O
service	O
which	O
does	O
not	O
perform	O
DNSSEC	B-Protocol
validation	O
,	O
principally	O
for	O
debugging	O
.	O
</s>
<s>
DNSSEC	B-Protocol
deployment	O
requires	O
software	O
on	O
the	O
server	O
and	O
client	O
side	O
.	O
</s>
<s>
Some	O
of	O
the	O
tools	O
that	O
support	O
DNSSEC	B-Protocol
include	O
:	O
</s>
<s>
Windows	B-Device
7	I-Device
and	O
Windows	B-Device
Server	I-Device
2008	I-Device
R2	I-Device
include	O
a	O
"	O
security-aware	O
"	O
stub	O
resolver	O
that	O
is	O
able	O
to	O
differentiate	O
between	O
secure	O
and	O
non-secure	O
responses	O
by	O
a	O
recursive	O
name	O
server	O
.	O
</s>
<s>
Windows	O
Server	O
2012	O
DNSSEC	B-Protocol
is	O
compatible	O
with	O
secure	O
dynamic	O
updates	O
with	O
Active	O
Directory-integrated	O
zones	O
,	O
plus	O
Active	O
Directory	O
replication	O
of	O
anchor	O
keys	O
to	O
other	O
such	O
servers	O
.	O
</s>
<s>
BIND	B-Protocol
,	O
the	O
most	O
popular	O
DNS	B-Protocol
name	I-Protocol
server	O
(	O
which	O
includes	O
dig	B-Protocol
)	O
,	O
incorporates	O
the	O
newer	O
DNSSEC-bis	B-Protocol
(	O
DS	O
records	O
)	O
protocol	O
as	O
well	O
as	O
support	O
for	O
NSEC3	O
records	O
.	O
</s>
<s>
Unbound	B-Protocol
is	O
a	O
DNS	B-Protocol
name	I-Protocol
server	O
that	O
was	O
written	O
from	O
the	O
ground	O
up	O
to	O
be	O
designed	O
around	O
DNSSEC	B-Protocol
concepts	O
.	O
</s>
<s>
mysqlbind	B-Protocol
The	O
GPL	O
DNS	B-Protocol
management	I-Protocol
software	I-Protocol
for	O
DNS	B-Application
ASPs	O
now	O
supports	O
DNSSEC	B-Protocol
.	O
</s>
<s>
OpenDNSSEC	B-Protocol
is	O
a	O
designated	O
DNSSEC	B-Protocol
signer	O
tool	O
using	O
PKCS	O
#11	O
to	O
interface	O
with	O
hardware	O
security	O
modules	O
.	O
</s>
<s>
Knot	B-Protocol
DNS	I-Protocol
has	O
added	O
support	O
for	O
automatic	O
DNSSEC	B-Protocol
signing	O
in	O
version	O
1.4.0	O
.	O
</s>
<s>
PowerDNS	B-Language
fully	O
supports	O
DNSSEC	B-Protocol
as	O
of	O
version	O
3.0	O
in	O
pre-signed	O
and	O
live-signed	O
modes	O
.	O
</s>
