<s>
Cryptocat	B-Protocol
is	O
a	O
discontinued	O
open-source	B-Application
desktop	B-Application
application	I-Application
intended	O
to	O
allow	O
encrypted	O
online	B-Protocol
chatting	I-Protocol
available	O
for	O
Windows	B-Application
,	O
OS	B-Operating_System
X	I-Operating_System
,	O
and	O
Linux	B-Application
.	O
</s>
<s>
It	O
uses	O
end-to-end	O
encryption	O
to	O
secure	O
all	O
communications	O
to	O
other	O
Cryptocat	B-Protocol
users	O
.	O
</s>
<s>
Cryptocat	B-Protocol
was	O
created	O
by	O
Nadim	O
Kobeissi	O
and	O
further	O
developed	O
along	O
with	O
a	O
community	O
of	O
open	O
source	O
contributors	O
and	O
is	O
published	O
under	O
the	O
terms	O
of	O
the	O
GPLv3	O
license	O
,	O
although	O
it	O
has	O
since	O
been	O
discontinued	O
.	O
</s>
<s>
Cryptocat	B-Protocol
was	O
first	O
launched	O
on	O
19	O
May	O
2011	O
as	O
a	O
web	B-Application
application	I-Application
.	O
</s>
<s>
In	O
June	O
2012	O
,	O
Kobeissi	O
said	O
he	O
was	O
detained	O
at	O
the	O
U.S.	O
border	O
by	O
the	O
DHS	O
and	O
questioned	O
about	O
Cryptocat	B-Protocol
's	O
censorship	O
resistance	O
.	O
</s>
<s>
In	O
June	O
2013	O
,	O
security	O
researcher	O
Steve	O
Thomas	O
pointed	O
out	O
a	O
security	O
bug	O
that	O
could	O
be	O
used	O
to	O
decrypt	O
any	O
group	O
chat	B-Protocol
message	O
that	O
had	O
taken	O
place	O
using	O
Cryptocat	B-Protocol
between	O
September	O
2012	O
and	O
19	O
April	O
2013	O
.	O
</s>
<s>
In	O
response	O
,	O
Cryptocat	B-Protocol
issued	O
a	O
security	O
advisory	O
,	O
requested	O
that	O
all	O
users	O
ensure	O
that	O
they	O
had	O
upgraded	O
,	O
and	O
informed	O
users	O
that	O
past	O
group	O
conversations	O
may	O
have	O
been	O
compromised	O
.	O
</s>
<s>
In	O
February	O
2014	O
,	O
an	O
audit	O
by	O
iSec	O
Partners	O
criticized	O
Cryptocat	B-Protocol
's	O
authentication	O
model	O
as	O
insufficient	O
.	O
</s>
<s>
In	O
response	O
,	O
Cryptocat	B-Protocol
made	O
improvements	O
to	O
user	O
authentication	O
,	O
making	O
it	O
easier	O
for	O
users	O
to	O
authenticate	O
and	O
detect	O
man-in-the-middle	O
attacks	O
.	O
</s>
<s>
In	O
February	O
2016	O
,	O
citing	O
dissatisfaction	O
with	O
the	O
project	O
's	O
current	O
state	O
after	O
19	O
months	O
of	O
non-maintenance	O
,	O
Kobeissi	O
announced	O
that	O
he	O
would	O
be	O
taking	O
Cryptocat	B-Protocol
temporarily	O
offline	O
and	O
discontinuing	O
the	O
development	O
of	O
its	O
mobile	O
application	O
,	O
pending	O
a	O
complete	O
rewrite	O
and	O
relaunch	O
of	O
the	O
software	O
.	O
</s>
<s>
In	O
March	O
2016	O
Kobeissi	O
announced	O
the	O
re-release	O
of	O
Cryptocat	B-Protocol
,	O
rewritten	O
completely	O
as	O
desktop	B-Application
software	I-Application
instead	O
of	O
the	O
original	O
web	B-Application
application	I-Application
software	O
,	O
as	O
a	O
public	O
beta	O
and	O
the	O
resumption	O
of	O
the	O
service	O
.	O
</s>
<s>
The	O
new	O
desktop-centric	O
approach	O
allowed	O
Cryptocat	B-Protocol
to	O
benefit	O
from	O
stronger	O
desktop	O
integration	O
,	O
in	O
a	O
style	O
similar	O
to	O
Pidgin	B-Protocol
.	O
</s>
<s>
In	O
February	O
2019	O
,	O
it	O
was	O
announced	O
that	O
Cryptocat	B-Protocol
would	O
be	O
discontinued	O
.	O
</s>
<s>
As	O
of	O
December	O
2019	O
,	O
the	O
cryptocat	B-Protocol
domain	O
is	O
for	O
sale	O
and	O
links	O
to	O
the	O
site	O
for	O
the	O
Wire	B-Application
messenger	I-Application
.	O
</s>
<s>
Cryptocat	B-Protocol
allows	O
its	O
users	O
to	O
set	O
up	O
end-to-end	O
encrypted	O
chat	B-Protocol
conversations	O
.	O
</s>
<s>
All	O
devices	O
linked	O
to	O
Cryptocat	B-Protocol
accounts	O
will	O
receive	O
forward	O
secure	O
messages	O
,	O
even	O
when	O
offline	O
.	O
</s>
<s>
All	O
messages	O
,	O
files	O
and	O
audio/video	O
recordings	O
sent	O
over	O
Cryptocat	B-Protocol
are	O
end-to-end	O
encrypted	O
.	O
</s>
<s>
Cryptocat	B-Protocol
users	O
link	O
their	O
devices	O
to	O
their	O
Cryptocat	B-Protocol
account	O
upon	O
connection	O
,	O
and	O
can	O
identify	O
each	O
other	O
's	O
devices	O
via	O
the	O
client	O
's	O
device	O
manager	O
in	O
order	O
to	O
prevent	O
man-in-the-middle	O
attacks	O
.	O
</s>
<s>
Cryptocat	B-Protocol
also	O
employs	O
a	O
Trust	O
on	O
first	O
use	O
mechanism	O
in	O
order	O
to	O
help	O
detect	O
device	O
identity	O
key	O
changes	O
.	O
</s>
<s>
Cryptocat	B-Protocol
also	O
includes	O
a	O
built-in	O
auto-update	O
mechanism	O
that	O
automatically	O
performs	O
a	O
signature	O
check	O
on	O
downloaded	O
updates	O
in	O
order	O
to	O
verify	O
authenticity	O
,	O
and	O
employs	O
TLS	B-Protocol
certificate	B-Protocol
pinning	I-Protocol
in	O
order	O
to	O
prevent	O
network	O
impersonation	O
attacks	O
.	O
</s>
<s>
Originally	O
in	O
2013	O
,	O
Cryptocat	B-Protocol
offered	O
the	O
ability	O
to	O
connect	O
to	O
Facebook	O
Messenger	O
to	O
initiate	O
encrypted	O
chatting	B-Protocol
with	O
other	O
Cryptocat	B-Protocol
users	O
.	O
</s>
<s>
According	O
to	O
the	O
developers	O
,	O
the	O
feature	O
was	O
meant	O
to	O
help	O
offer	O
an	O
alternative	O
to	O
the	O
regular	O
Cryptocat	B-Protocol
chat	B-Protocol
model	O
which	O
did	O
not	O
offer	O
long-term	O
contact	O
lists	O
.	O
</s>
<s>
In	O
June	O
2013	O
,	O
Cryptocat	B-Protocol
was	O
used	O
by	O
journalist	O
Glenn	O
Greenwald	O
while	O
in	O
Hong	O
Kong	O
to	O
meet	O
NSA	O
whistleblower	O
Edward	O
Snowden	O
for	O
the	O
first	O
time	O
,	O
after	O
other	O
encryption	O
software	O
failed	O
to	O
work	O
.	O
</s>
<s>
In	O
November	O
2013	O
,	O
Cryptocat	B-Protocol
was	O
banned	O
in	O
Iran	O
,	O
shortly	O
after	O
the	O
election	O
of	O
Iran	O
's	O
new	O
president	O
Hassan	O
Rouhani	O
who	O
had	O
promised	O
more	O
open	O
Internet	O
laws	O
.	O
</s>
<s>
Cryptocat	B-Protocol
was	O
listed	O
on	O
the	O
Electronic	O
Frontier	O
Foundation	O
's	O
"	O
Secure	O
Messaging	O
Scorecard	O
"	O
from	O
4	O
November	O
2014	O
until	O
13	O
March	O
2016	O
.	O
</s>
<s>
During	O
that	O
time	O
,	O
Cryptocat	B-Protocol
had	O
a	O
score	O
of	O
7	O
out	O
of	O
7	O
points	O
on	O
the	O
scorecard	O
.	O
</s>
<s>
It	O
had	O
received	O
points	O
for	O
having	O
communications	O
encrypted	O
in	O
transit	O
,	O
having	O
communications	O
encrypted	O
with	O
keys	O
the	O
provider	O
did	O
not	O
have	O
access	O
to	O
(	O
end-to-end	O
encryption	O
)	O
,	O
making	O
it	O
possible	O
for	O
users	O
to	O
independently	O
verify	O
their	O
correspondent	O
's	O
identities	O
,	O
having	O
past	O
communications	O
secure	O
if	O
the	O
keys	O
were	O
stolen	O
(	O
forward	O
secrecy	O
)	O
,	O
having	O
its	O
code	O
open	O
to	O
independent	O
review	O
(	O
open-source	B-Application
)	O
,	O
having	O
its	O
security	O
designs	O
well-documented	O
,	O
and	O
having	O
completed	O
an	O
independent	O
security	O
audit	O
.	O
</s>
<s>
Cryptocat	B-Protocol
uses	O
a	O
Double	B-Algorithm
Ratchet	I-Algorithm
Algorithm	I-Algorithm
in	O
order	O
to	O
obtain	O
forward	O
and	O
future	O
secrecy	O
across	O
messages	O
,	O
after	O
a	O
session	O
is	O
established	O
using	O
a	O
four-way	O
Elliptic-curve	B-Protocol
Diffie	I-Protocol
–	I-Protocol
Hellman	I-Protocol
handshake	O
.	O
</s>
<s>
The	O
approach	O
is	O
similar	O
to	O
the	O
encryption	O
protocol	O
adopted	O
for	O
encrypted	O
messaging	O
by	O
the	O
Signal	B-Application
mobile	O
application	O
.	O
</s>
<s>
Cryptocat	B-Protocol
's	O
goal	O
is	O
for	O
its	O
messages	O
to	O
obtain	O
confidentiality	O
,	O
integrity	O
,	O
source	O
authenticity	O
,	O
forward	O
and	O
future	O
secrecy	O
and	O
indistinguishability	O
even	O
over	O
a	O
network	O
controlled	O
by	O
an	O
active	O
attacker	O
.	O
</s>
<s>
The	O
forward	O
secrecy	O
features	O
of	O
the	O
protocol	O
that	O
Cryptocat	B-Protocol
uses	O
are	O
similar	O
to	O
those	O
first	O
introduced	O
by	O
Off-the-Record	B-Protocol
Messaging	I-Protocol
.	O
</s>
<s>
Cryptocat	B-Protocol
uses	O
the	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
in	O
Galois/Counter	B-Algorithm
Mode	I-Algorithm
for	O
authenticated	O
encryption	O
,	O
Curve25519	O
for	O
Elliptic	B-Protocol
curve	I-Protocol
Diffie-Hellman	I-Protocol
shared	O
secret	O
agreement	O
,	O
HMAC-SHA256	B-Algorithm
for	O
key	O
derivation	O
and	O
Ed25519	O
for	O
signing	O
.	O
</s>
<s>
In	O
order	O
to	O
limit	O
the	O
effect	O
of	O
a	O
long-term	O
identity	O
key	O
compromise	O
,	O
long-term	O
keys	O
are	O
used	O
exclusively	O
once	O
for	O
the	O
initial	O
Authenticated	B-General_Concept
Key	I-General_Concept
Exchange	I-General_Concept
,	O
and	O
once	O
for	O
signing	O
a	O
newly	O
generated	O
intermediate-term	O
signed	O
prekey	O
.	O
</s>
<s>
For	O
the	O
transport	O
layer	O
,	O
Cryptocat	B-Protocol
adopts	O
the	O
OMEMO	B-Application
Multi-End	I-Application
Message	I-Application
and	I-Application
Object	I-Application
Encryption	I-Application
standard	O
,	O
which	O
also	O
gives	O
Cryptocat	B-Protocol
multi-device	O
support	O
and	O
allows	O
for	O
offline	O
messaging	O
.	O
</s>
<s>
Cryptocat	B-Protocol
's	O
network	O
relies	O
on	O
a	O
XMPP	B-Protocol
configuration	O
served	O
over	O
WebSockets	B-Protocol
.	O
</s>
<s>
According	O
to	O
the	O
project	O
's	O
mission	O
statement	O
,	O
Cryptocat	B-Protocol
's	O
network	O
only	O
relays	O
encrypted	O
messages	O
and	O
does	O
not	O
store	O
any	O
data	O
.	O
</s>
<s>
In	O
addition	O
to	O
the	O
Cryptocat	B-Protocol
client	O
's	O
end-to-end	O
encryption	O
protocol	O
,	O
client-server	O
communication	O
is	O
protected	O
by	O
TLS	B-Protocol
.	O
</s>
<s>
From	O
March	O
2011	O
until	O
March	O
2016	O
,	O
Cryptocat	B-Protocol
was	O
officially	O
distributed	O
through	O
the	O
Google	B-Application
Chrome	I-Application
Web	I-Application
Store	I-Application
,	O
the	O
Apple	B-Application
App	I-Application
Store	I-Application
and	O
other	O
official	O
channels	O
controlled	O
by	O
targeted	O
platforms	O
.	O
</s>
<s>
After	O
Cryptocat	B-Protocol
's	O
re-write	O
into	O
desktop	B-Application
software	I-Application
in	O
March	O
2016	O
,	O
the	O
software	O
became	O
distributed	O
exclusively	O
through	O
Cryptocat	B-Protocol
's	O
own	O
servers	O
,	O
which	O
also	O
handle	O
signed	O
update	O
delivery	O
.	O
</s>
