<s>
DNSCrypt	B-Protocol
is	O
a	O
network	O
protocol	O
that	O
authenticates	O
and	O
encrypts	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
traffic	O
between	O
the	O
user	O
's	O
computer	O
and	O
recursive	O
name	B-Protocol
servers	I-Protocol
.	O
</s>
<s>
It	O
is	O
available	O
for	O
a	O
variety	O
of	O
operating	O
systems	O
,	O
including	O
Unix	O
,	O
Apple	O
iOS	O
,	O
Linux	B-Application
,	O
Android	O
,	O
and	O
Microsoft	O
Windows	O
.	O
</s>
<s>
DNSCrypt	B-Protocol
wraps	O
unmodified	O
DNS	B-Protocol
traffic	O
between	O
a	O
client	O
and	O
a	O
DNS	B-Protocol
resolver	O
in	O
a	O
cryptographic	O
construction	O
in	O
order	O
to	O
detect	O
forgery	O
.	O
</s>
<s>
The	O
free	O
and	O
open	O
source	O
software	O
implementation	O
dnscrypt-proxy	O
additionally	O
integrates	O
ODoH	O
.	O
</s>
<s>
It	O
also	O
mitigates	O
UDP-based	O
amplification	O
attacks	O
by	O
requiring	O
a	O
question	O
to	O
be	O
at	O
least	O
as	O
large	O
as	O
the	O
corresponding	O
response	O
.	O
</s>
<s>
Thus	O
,	O
DNSCrypt	B-Protocol
helps	O
to	O
prevent	O
DNS	B-Protocol
amplification	O
attacks	O
.	O
</s>
<s>
In	O
addition	O
to	O
private	O
deployments	O
,	O
the	O
DNSCrypt	B-Protocol
protocol	O
has	O
been	O
adopted	O
by	O
several	O
public	O
DNS	B-Protocol
resolvers	O
,	O
the	O
vast	O
majority	O
being	O
members	O
of	O
the	O
OpenNIC	B-Protocol
network	O
,	O
as	O
well	O
as	O
virtual	B-Application
private	I-Application
network	I-Application
(	O
VPN	B-Application
)	O
services	O
.	O
</s>
<s>
OpenDNS	B-Protocol
(	O
now	O
a	O
part	O
of	O
Cisco	O
)	O
announced	O
the	O
first	O
public	O
DNS	B-Protocol
service	O
supporting	O
DNSCrypt	B-Protocol
on	O
6	O
December	O
2011	O
,	O
shortly	O
followed	O
by	O
CloudNS	O
Australia	O
.	O
</s>
<s>
On	O
29	O
March	O
2016	O
,	O
Yandex	O
announced	O
support	O
for	O
the	O
DNSCrypt	B-Protocol
protocol	O
on	O
their	O
public	O
DNS	B-Protocol
servers	I-Protocol
,	O
as	O
well	O
as	O
in	O
Yandex	B-Language
Browser	I-Language
.	O
</s>
<s>
On	O
14	O
October	O
2016	O
,	O
AdGuard	B-Application
added	O
DNSCrypt	B-Protocol
to	O
their	O
DNS	B-Protocol
filtering	O
module	O
so	O
that	O
users	O
could	O
move	O
from	O
their	O
ISPs	O
to	O
custom	O
or	O
AdGuard	B-Application
's	O
own	O
DNS	B-Protocol
servers	I-Protocol
for	O
online	O
privacy	O
and	O
ad	O
blocking	O
.	O
</s>
<s>
On	O
10	O
September	O
2018	O
,	O
the	O
Quad9	B-Protocol
nonprofit	O
public	O
recursive	O
resolver	O
service	O
announced	O
support	O
for	O
DNSCrypt	B-Protocol
.	O
</s>
<s>
Other	O
servers	O
that	O
support	O
secure	O
protocol	O
are	O
mentioned	O
in	O
the	O
DNSCrypt	B-Protocol
creators’	O
list	O
.	O
</s>
<s>
DNSCrypt	B-Protocol
can	O
be	O
used	O
either	O
over	O
UDP	B-Protocol
or	O
over	O
TCP	B-Protocol
.	O
</s>
<s>
In	O
both	O
cases	O
,	O
its	O
default	O
port	B-Protocol
is	O
443	O
.	O
</s>
<s>
Even	O
though	O
the	O
protocol	O
radically	O
differs	O
from	O
HTTPS	B-Protocol
,	O
both	O
service	O
types	O
utilize	O
the	O
same	O
port	B-Protocol
.	O
</s>
<s>
However	O
,	O
even	O
though	O
DNS	B-Protocol
over	I-Protocol
HTTPS	I-Protocol
and	O
DNSCrypt	B-Protocol
are	O
possible	O
on	O
the	O
same	O
port	B-Protocol
,	O
they	O
must	O
still	O
run	O
separately	O
on	O
different	O
servers	O
.	O
</s>
<s>
Two	O
server	O
applications	O
cannot	O
run	O
simultaneously	O
on	O
the	O
same	O
server	O
if	O
both	O
utilize	O
the	O
same	O
port	B-Protocol
for	O
communication	O
;	O
though	O
a	O
multiplexing	O
approach	O
is	O
theoretically	O
possible	O
.	O
</s>
<s>
Instead	O
of	O
relying	O
on	O
trusted	O
certificate	B-Architecture
authorities	I-Architecture
commonly	O
found	O
in	O
web	O
browsers	O
,	O
the	O
client	O
has	O
to	O
explicitly	O
trust	O
the	O
public	O
signing	O
key	O
of	O
the	O
chosen	O
provider	O
.	O
</s>
<s>
This	O
public	O
key	O
is	O
used	O
to	O
verify	O
a	O
set	O
of	O
certificates	O
,	O
retrieved	O
using	O
conventional	O
DNS	B-Protocol
queries	I-Protocol
.	O
</s>
<s>
The	O
DNSCrypt	B-Protocol
protocol	O
can	O
also	O
be	O
used	O
for	O
access	O
control	O
or	O
accounting	O
,	O
by	O
accepting	O
only	O
a	O
predefined	O
set	O
of	O
public	O
keys	O
.	O
</s>
<s>
This	O
can	O
be	O
used	O
by	O
commercial	O
DNS	B-Protocol
services	O
to	O
identify	O
customers	O
without	O
having	O
to	O
rely	O
on	O
IP	O
addresses	O
.	O
</s>
<s>
Over	O
UDP	B-Protocol
,	O
when	O
a	O
response	O
would	O
be	O
larger	O
than	O
the	O
question	O
leading	O
to	O
it	O
,	O
a	O
server	O
can	O
respond	O
with	O
a	O
short	O
packet	O
whose	O
TC	O
(	O
truncated	O
)	O
bit	O
has	O
been	O
set	O
.	O
</s>
<s>
The	O
client	O
should	O
then	O
retry	O
using	O
TCP	B-Protocol
and	O
increase	O
the	O
padding	O
of	O
subsequent	O
queries	O
.	O
</s>
<s>
Versions	O
1	O
and	O
2	O
of	O
the	O
protocol	O
use	O
the	O
X25519	B-Application
algorithm	O
for	O
key	O
exchange	O
,	O
EdDSA	B-Algorithm
for	O
signatures	O
,	O
as	O
well	O
as	O
XSalsa20-Poly1305	O
or	O
XChaCha20-Poly1305	O
for	O
authenticated	O
encryption	O
.	O
</s>
<s>
As	O
of	O
2023	O
,	O
there	O
are	O
no	O
known	O
vulnerabilities	O
in	O
the	O
DNSCrypt	B-Protocol
protocol	O
nor	O
practical	O
attacks	O
against	O
its	O
underlying	O
cryptographic	O
constructions	O
.	O
</s>
<s>
Anonymized	O
DNSCrypt	B-Protocol
is	O
a	O
protocol	O
extension	O
proposed	O
in	O
2019	O
to	O
further	O
improve	O
DNS	B-Protocol
privacy	O
.	O
</s>
<s>
Anonymized	O
DNSCrypt	B-Protocol
is	O
a	O
lightweight	O
alternative	O
to	O
Tor	O
and	O
SOCKS	O
proxies	O
,	O
specifically	O
designed	O
for	O
DNS	B-Protocol
traffic	O
.	O
</s>
<s>
Deployment	O
of	O
Anonymized	O
DNSCrypt	B-Protocol
started	O
in	O
October	O
2019	O
,	O
and	O
the	O
protocol	O
adoption	O
was	O
fast	O
,	O
with	O
40	O
DNS	B-Protocol
relays	O
being	O
set	O
up	O
only	O
two	O
weeks	O
after	O
the	O
public	O
availability	O
of	O
client	O
and	O
server	O
implementations	O
.	O
</s>
