<s>
DNSCurve	B-Protocol
is	O
a	O
proposed	O
secure	O
protocol	O
for	O
the	O
Domain	B-Protocol
Name	I-Protocol
System	I-Protocol
(	O
DNS	B-Protocol
)	O
,	O
designed	O
by	O
Daniel	O
J	O
.	O
Bernstein	O
.	O
</s>
<s>
DNSCurve	B-Protocol
uses	O
Curve25519	O
elliptic	O
curve	O
cryptography	O
to	O
establish	O
keys	O
used	O
by	O
Salsa20	B-Algorithm
,	O
paired	O
with	O
the	O
message	B-Algorithm
authentication	I-Algorithm
code	I-Algorithm
(	O
MAC	O
)	O
function	O
Poly1305	B-Algorithm
,	O
to	O
encrypt	O
and	O
authenticate	O
DNS	B-Protocol
packets	B-Protocol
between	O
resolvers	O
and	O
authoritative	O
servers	O
.	O
</s>
<s>
Public	B-Application
keys	I-Application
for	O
remote	O
authoritative	O
servers	O
are	O
placed	O
in	O
NS	O
records	O
,	O
so	O
recursive	O
resolvers	O
know	O
whether	O
the	O
server	O
supports	O
DNSCurve	B-Protocol
.	O
</s>
<s>
Keys	O
begin	O
with	O
the	O
magic	O
string	O
uz5	O
and	O
are	O
followed	O
by	O
a	O
51-byte	O
Base32	O
encoding	O
of	O
the	O
server	O
's	O
255-bit	O
public	B-Application
key	I-Application
.	O
</s>
<s>
E.g.	O
,	O
in	O
BIND	B-Protocol
format	O
:	O
</s>
<s>
The	O
resolver	O
then	O
sends	O
to	O
the	O
server	O
a	O
packet	B-Protocol
containing	O
its	O
DNSCurve	B-Protocol
public	B-Application
key	I-Application
,	O
a	O
96-bit	O
nonce	O
,	O
and	O
a	O
cryptographic	O
box	O
containing	O
the	O
query	O
.	O
</s>
<s>
The	O
cryptographic	O
box	O
is	O
created	O
using	O
the	O
resolver	O
's	O
private	B-Application
key	I-Application
,	O
the	O
server	O
's	O
public	B-Application
key	I-Application
,	O
and	O
the	O
nonce	O
.	O
</s>
<s>
The	O
cryptographic	O
tools	O
used	O
in	O
DNSCurve	B-Protocol
are	O
the	O
same	O
used	O
in	O
CurveCP	B-Protocol
,	O
a	O
UDP-based	O
protocol	O
which	O
is	O
similar	O
to	O
TCP	B-Protocol
but	O
uses	O
elliptic-curve	O
cryptography	O
to	O
encrypt	O
and	O
authenticate	O
data	O
.	O
</s>
<s>
An	O
analogy	O
is	O
that	O
while	O
DNSSEC	B-Protocol
is	O
like	O
signing	O
a	O
webpage	O
with	O
Pretty	B-Application
Good	I-Application
Privacy	I-Application
(	O
PGP	O
)	O
,	O
CurveCP	B-Protocol
and	O
DNSCurve	B-Protocol
are	O
like	O
encrypting	O
and	O
authenticating	O
the	O
channel	O
using	O
Transport	B-Protocol
Layer	I-Protocol
Security	I-Protocol
(	O
TLS	O
)	O
.	O
</s>
<s>
Just	O
as	O
PGP-signed	O
webpages	O
can	O
be	O
sent	O
over	O
an	O
encrypted	O
channel	O
using	O
SSL	O
,	O
DNSSEC	B-Protocol
data	O
can	O
be	O
protected	O
using	O
DNSCurve	B-Protocol
.	O
</s>
<s>
DNSCurve	B-Protocol
claims	O
advantages	O
over	O
previous	O
DNS	B-Protocol
services	O
of	O
:	O
</s>
<s>
Confidentiality	O
—	O
usual	O
DNS	B-Protocol
requests	O
and	O
responses	O
are	O
not	O
encrypted	O
,	O
and	O
broadcast	O
to	O
any	O
attacker	O
.	O
</s>
<s>
Integrity	O
—	O
usual	O
DNS	B-Protocol
has	O
some	O
protection	O
,	O
but	O
with	O
patience	O
and	O
sniffing	O
attackers	O
can	O
forge	O
DNS	B-Protocol
records	O
;	O
this	O
is	O
prevented	O
by	O
DNSCurve	B-Protocol
cryptographic	O
authentication	O
.	O
</s>
<s>
Availability	O
—	O
usual	O
DNS	B-Protocol
has	O
no	O
protection	O
against	O
denial	O
of	O
service	O
(	O
DoS	O
)	O
by	O
a	O
sniffing	O
attacker	O
sending	O
a	O
few	O
forged	O
packets	B-Protocol
per	O
second	O
.	O
</s>
<s>
DNSCurve	B-Protocol
recognizes	O
and	O
discards	O
forged	O
DNS	B-Protocol
packets	B-Protocol
,	O
providing	O
some	O
protection	O
,	O
though	O
SMTP	O
,	O
HTTP	O
,	O
HTTPS	O
,	O
are	O
also	O
vulnerable	O
to	O
DoS	O
.	O
</s>
<s>
DNSCurve	B-Protocol
uses	O
256-bit	O
elliptic-curve	O
cryptography	O
,	O
which	O
NIST	O
estimates	O
to	O
be	O
roughly	O
equivalent	O
to	O
3072-bit	O
RSA	O
.	O
</s>
<s>
It	O
uses	O
per-query	O
public-key	B-Application
crypto	O
(	O
like	O
SSH	O
and	O
SSL	O
)	O
,	O
and	O
96-bit	O
nonces	O
to	O
protect	O
against	O
replay	O
attacks	O
.	O
</s>
<s>
Adam	O
Langley	O
has	O
posted	O
speed	O
tests	O
on	O
his	O
personal	O
website	O
showing	O
Curve25519	O
,	O
used	O
by	O
DNSCurve	B-Protocol
,	O
to	O
be	O
the	O
fastest	O
among	O
elliptic	O
curves	O
tested	O
.	O
</s>
<s>
DNSCurve	B-Protocol
first	O
gained	O
recursive	O
support	O
in	O
dnscache	O
via	O
a	O
patch	O
by	O
Matthew	O
Dempsky	O
.	O
</s>
<s>
Dempsky	O
also	O
has	O
a	O
GitHub	B-Application
repository	O
which	O
includes	O
Python	O
DNS	B-Protocol
lookup	O
tools	O
and	O
a	O
forwarder	O
in	O
C	O
.	O
Adam	O
Langley	O
has	O
a	O
GitHub	B-Application
repository	O
as	O
well	O
.	O
</s>
<s>
There	O
is	O
an	O
authoritative	O
forwarder	O
called	O
CurveDNS	O
which	O
allows	O
DNS	B-Protocol
administrators	O
to	O
protect	O
existing	O
installations	O
without	O
patching	O
.	O
</s>
<s>
OpenDNS	B-Protocol
has	O
released	O
DNSCrypt	B-Protocol
to	O
protect	O
the	O
channel	O
between	O
OpenDNS	B-Protocol
's	O
users	O
and	O
its	O
recursive	O
resolvers	O
.	O
</s>
<s>
Jan	O
Mojžíš	O
has	O
released	O
curveprotect	O
,	O
a	O
software	O
suite	O
which	O
implements	O
DNSCurve	B-Protocol
and	O
CurveCP	B-Protocol
protection	O
for	O
common	O
services	O
like	O
DNS	B-Protocol
,	O
SSH	O
,	O
HTTP	O
,	O
and	O
SMTP	O
.	O
</s>
<s>
OpenDNS	B-Protocol
,	O
which	O
has	O
50	O
million	O
users	O
,	O
announced	O
support	O
for	O
DNSCurve	B-Protocol
on	O
its	O
recursive	O
resolvers	O
on	O
February	O
23	O
,	O
2010	O
.	O
</s>
<s>
Then	O
on	O
December	O
6	O
,	O
2011	O
,	O
OpenDNS	B-Protocol
announced	O
a	O
new	O
tool	O
,	O
called	O
DNSCrypt	B-Protocol
.	O
</s>
<s>
DNSCrypt	B-Protocol
protects	O
the	O
channel	O
between	O
OpenDNS	B-Protocol
and	O
its	O
users	O
.	O
</s>
<s>
No	O
equally	O
large	O
authoritative	O
DNS	B-Protocol
providers	O
have	O
yet	O
deployed	O
DNSCurve	B-Protocol
.	O
</s>
