<s>
SILC	B-Protocol
(	O
Secure	O
Internet	O
Live	O
Conferencing	O
protocol	O
)	O
is	O
a	O
protocol	O
that	O
provides	O
secure	O
synchronous	B-Protocol
conferencing	I-Protocol
services	O
(	O
very	O
much	O
like	O
IRC	B-Protocol
)	O
over	O
the	O
Internet	O
.	O
</s>
<s>
The	O
SILC	B-Protocol
protocol	I-Protocol
can	O
be	O
divided	O
in	O
three	O
main	O
parts	O
:	O
SILC	B-Protocol
Key	O
Exchange	O
(	O
SKE	O
)	O
protocol	O
,	O
SILC	B-Protocol
Authentication	O
protocol	O
and	O
SILC	B-Protocol
Packet	B-Protocol
protocol	O
.	O
</s>
<s>
SILC	B-Protocol
protocol	I-Protocol
additionally	O
defines	O
SILC	B-Protocol
Commands	O
that	O
are	O
used	O
to	O
manage	O
the	O
SILC	B-Protocol
session	O
.	O
</s>
<s>
SILC	B-Protocol
provides	O
channels	O
(	O
groups	O
)	O
,	O
nicknames	O
,	O
private	O
messages	O
,	O
and	O
other	O
common	O
features	O
.	O
</s>
<s>
However	O
,	O
SILC	B-Protocol
nicknames	O
,	O
in	O
contrast	O
to	O
many	O
other	O
protocols	O
(	O
e.g.	O
</s>
<s>
IRC	B-Protocol
)	O
,	O
are	O
not	O
unique	O
;	O
a	O
user	O
is	O
able	O
to	O
use	O
any	O
nickname	O
,	O
even	O
if	O
one	O
is	O
already	O
in	O
use	O
.	O
</s>
<s>
The	O
real	O
identification	O
in	O
the	O
protocol	O
is	O
performed	O
by	O
unique	O
Client	B-Protocol
ID	O
.	O
</s>
<s>
The	O
SILC	B-Protocol
protocol	I-Protocol
uses	O
this	O
to	O
overcome	O
nickname	O
collision	O
,	O
a	O
problem	O
present	O
in	O
many	O
other	O
protocols	O
.	O
</s>
<s>
All	O
messages	O
sent	O
in	O
a	O
SILC	B-Protocol
network	O
are	O
binary	O
,	O
allowing	O
them	O
to	O
contain	O
any	O
type	O
of	O
data	O
,	O
including	O
text	O
,	O
video	O
,	O
audio	O
,	O
and	O
other	O
multimedia	O
data	O
.	O
</s>
<s>
The	O
SKE	O
protocol	O
is	O
used	O
to	O
establish	O
session	O
key	O
and	O
other	O
security	O
parameters	O
for	O
protecting	O
the	O
SILC	B-Protocol
Packet	B-Protocol
protocol	O
.	O
</s>
<s>
The	O
SKE	O
itself	O
is	O
based	O
on	O
the	O
Diffie	B-Protocol
–	I-Protocol
Hellman	I-Protocol
key	I-Protocol
exchange	I-Protocol
algorithm	O
(	O
a	O
form	O
of	O
asymmetric	B-Application
cryptography	I-Application
)	O
and	O
the	O
exchange	O
is	O
protected	O
with	O
digital	O
signatures	O
.	O
</s>
<s>
The	O
SILC	B-Protocol
Authentication	O
protocol	O
is	O
performed	O
after	O
successful	O
SKE	O
protocol	O
execution	O
to	O
authenticate	O
a	O
client	B-Protocol
and/or	O
a	O
server	B-Application
.	O
</s>
<s>
The	O
authentication	O
may	O
be	O
based	O
on	O
passphrase	O
or	O
on	O
digital	O
signatures	O
,	O
and	O
if	O
successful	O
gives	O
access	O
to	O
the	O
relevant	O
SILC	B-Protocol
network	O
.	O
</s>
<s>
The	O
SILC	B-Protocol
Packet	B-Protocol
protocol	O
is	O
intended	O
to	O
be	O
a	O
secure	O
binary	O
packet	B-Protocol
protocol	O
,	O
assuring	O
that	O
the	O
content	O
of	O
each	O
packet	B-Protocol
(	O
consisting	O
of	O
a	O
packet	B-Protocol
header	O
and	O
packet	B-Protocol
payload	O
)	O
is	O
secured	O
and	O
authenticated	O
.	O
</s>
<s>
The	O
packets	B-Protocol
are	O
secured	O
using	O
algorithms	O
based	O
on	O
symmetric	B-Algorithm
cryptography	I-Algorithm
and	O
authenticated	O
by	O
using	O
Message	B-Algorithm
Authentication	I-Algorithm
Code	I-Algorithm
algorithm	O
,	O
HMAC	B-Algorithm
.	O
</s>
<s>
SILC	B-Protocol
channels	O
(	O
groups	O
)	O
are	O
protected	O
by	O
using	O
symmetric	O
channel	O
keys	O
.	O
</s>
<s>
Private	O
messages	O
between	O
users	O
in	O
a	O
SILC	B-Protocol
network	O
are	O
protected	O
with	O
session	O
keys	O
.	O
</s>
<s>
When	O
messages	O
are	O
secured	O
with	O
key	O
material	O
generated	O
with	O
the	O
SKE	O
protocol	O
or	O
previously	O
agreed	O
upon	O
key	O
material	O
(	O
for	O
example	O
,	O
passphrases	O
)	O
SILC	B-Protocol
provides	O
security	O
even	O
when	O
the	O
SILC	B-Protocol
server	B-Application
may	O
be	O
compromised	O
.	O
</s>
<s>
SILC	B-Protocol
was	O
designed	O
by	O
Pekka	O
Riikonen	O
between	O
1996	O
and	O
1999	O
and	O
first	O
released	O
in	O
public	O
in	O
summer	O
2000	O
.	O
</s>
<s>
A	O
client	B-Protocol
and	O
a	O
server	B-Application
were	O
written	O
.	O
</s>
<s>
At	O
present	O
time	O
,	O
there	O
are	O
several	O
clients	O
,	O
the	O
most	O
advanced	O
being	O
the	O
official	O
SILC	B-Protocol
client	B-Protocol
and	O
an	O
irssi	B-Protocol
plugin	O
.	O
</s>
<s>
SILC	B-Protocol
protocol	I-Protocol
is	O
also	O
integrated	O
to	O
the	O
popular	O
Pidgin	B-Protocol
instant	O
messaging	O
client	B-Protocol
.	O
</s>
<s>
Other	O
GUI	B-Application
clients	O
are	O
Silky	O
and	O
Colloquy	B-Language
.	O
</s>
<s>
The	O
Silky	O
client	B-Protocol
was	O
put	O
on	O
hold	O
and	O
abandoned	O
on	O
the	O
18th	O
of	O
July	O
2007	O
,	O
due	O
to	O
inactivity	O
for	O
several	O
years	O
.	O
</s>
<s>
The	O
latest	O
news	O
on	O
the	O
Silky	O
website	O
was	O
that	O
the	O
client	B-Protocol
was	O
to	O
be	O
completely	O
rewritten	O
.	O
</s>
<s>
As	O
of	O
2008	O
,	O
three	O
SILC	B-Protocol
protocol	I-Protocol
implementations	O
have	O
been	O
written	O
.	O
</s>
<s>
Most	O
SILC	B-Protocol
clients	O
use	O
libsilc	O
,	O
part	O
of	O
the	O
SILC	B-Protocol
Toolkit	O
.	O
</s>
<s>
The	O
SILC	B-Protocol
Toolkit	O
is	O
dual-licensed	O
and	O
distributed	O
under	O
both	O
the	O
GNU	O
General	O
Public	O
License	O
(	O
GPL	O
)	O
and	O
the	O
revised	O
BSD	O
license	O
.	O
</s>
<s>
As	O
described	O
in	O
the	O
SILC	B-Protocol
FAQ	O
,	O
chats	O
are	O
secured	O
through	O
the	O
generation	O
of	O
symmetric	B-Algorithm
encryption	I-Algorithm
keys	O
.	O
</s>
<s>
These	O
keys	O
have	O
to	O
be	O
generated	O
somewhere	O
,	O
and	O
this	O
occurs	O
on	O
the	O
server	B-Application
.	O
</s>
<s>
This	O
means	O
that	O
chats	O
might	O
be	O
compromised	O
,	O
if	O
the	O
server	B-Application
itself	O
is	O
compromised	O
.	O
</s>
<s>
The	O
solution	O
offered	O
is	O
that	O
chat	O
members	O
generate	O
their	O
own	O
public-private	O
keypair	B-Application
for	O
asymmetric	B-Application
encryption	I-Application
.	O
</s>
<s>
The	O
private	B-Application
key	I-Application
is	O
shared	O
only	O
by	O
the	O
chat	O
members	O
,	O
and	O
this	O
is	O
done	O
out	O
of	O
band	O
.	O
</s>
<s>
The	O
public	B-Application
key	I-Application
is	O
used	O
to	O
encrypt	O
messages	O
into	O
the	O
channel	O
.	O
</s>
<s>
This	O
approach	O
is	O
still	O
open	O
to	O
compromise	O
,	O
if	O
one	O
of	O
the	O
members	O
of	O
the	O
chat	O
should	O
have	O
their	O
private	B-Application
key	I-Application
compromised	O
,	O
or	O
if	O
they	O
should	O
share	O
the	O
key	O
with	O
another	O
,	O
without	O
agreement	O
of	O
the	O
group	O
.	O
</s>
<s>
SILC	B-Protocol
uses	O
a	O
similar	O
pattern	O
to	O
IRC	B-Protocol
,	O
in	O
that	O
there	O
is	O
no	O
global	O
"	O
SILC	B-Protocol
network	O
"	O
but	O
many	O
small	O
independent	O
networks	O
consisting	O
of	O
one	O
or	O
several	O
servers	O
each	O
,	O
although	O
it	O
is	O
claimed	O
that	O
SILC	B-Protocol
can	O
scale	O
better	O
with	O
many	O
servers	O
in	O
a	O
single	O
network	O
.	O
</s>
<s>
However	O
,	O
as	O
of	O
May	O
2014	O
,	O
it	O
has	O
only	O
one	O
active	O
(	O
though	O
unstable	O
)	O
server	B-Application
out	O
of	O
four	O
.	O
</s>
<s>
Most	O
SILC	B-Protocol
networks	O
have	O
shut	O
down	O
due	O
to	O
declining	O
popularity	O
of	O
SILC	B-Protocol
.	O
</s>
