<s>
Retroshare	B-Application
is	O
a	O
free	B-License
and	I-License
open-source	I-License
peer-to-peer	O
communication	O
and	O
file	O
sharing	O
app	O
based	O
on	O
a	O
friend-to-friend	O
network	O
built	O
by	O
GNU	B-Application
Privacy	I-Application
Guard	I-Application
(	O
GPG	B-Application
)	O
.	O
</s>
<s>
Optionally	O
,	O
peers	O
may	O
exchange	O
certificates	O
and	O
IP	B-Protocol
addresses	I-Protocol
to	O
their	O
friends	O
and	O
vice	O
versa	O
.	O
</s>
<s>
Retroshare	B-Application
was	O
founded	O
in	O
2004	O
by	O
Mark	O
Fernie	O
.	O
</s>
<s>
An	O
unofficial	O
build	O
for	O
the	O
single-board	B-Device
computer	I-Device
Raspberry	B-Operating_System
Pi	I-Operating_System
,	O
named	O
PiShare	O
,	O
since	O
2012	O
.	O
</s>
<s>
On	O
4	O
November	O
2014	O
,	O
Retroshare	B-Application
scored	O
6	O
out	O
of	O
7	O
points	O
on	O
the	O
Electronic	O
Frontier	O
Foundation	O
's	O
secure	O
messaging	O
scorecard	O
,	O
which	O
is	O
now	O
out-of-date	O
.	O
</s>
<s>
In	O
August	O
2015	O
,	O
Retroshare	B-Application
repository	B-Protocol
was	O
migrated	O
from	O
SourceForge	B-Application
to	O
GitHub	B-Application
.	O
</s>
<s>
In	O
2016	O
,	O
Linux	B-Application
Magazine	O
reviewed	O
security	O
gaps	O
in	O
Retroshare	B-Application
and	O
described	O
it	O
as	O
"	O
a	O
brave	O
effort	O
,	O
but	O
,	O
in	O
the	O
end	O
,	O
an	O
ineffective	O
one.	O
"	O
</s>
<s>
Retroshare	B-Application
is	O
an	O
instant	B-Application
messaging	I-Application
and	O
file-sharing	O
network	O
that	O
uses	O
a	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
for	O
address	O
discovery	O
.	O
</s>
<s>
After	O
initial	O
installation	O
,	O
the	O
user	O
generates	O
a	O
pair	O
of	O
(	O
GPG	B-Application
)	O
cryptographic	O
keys	O
with	O
Retroshare	B-Application
.	O
</s>
<s>
After	O
authentication	O
and	O
exchanging	O
an	O
asymmetric	B-Application
key	I-Application
,	O
OpenSSL	B-Language
is	O
used	O
to	O
establish	O
a	O
connection	O
,	O
and	O
for	O
end-to-end	O
encryption	O
.	O
</s>
<s>
IPv6	B-Protocol
support	O
was	O
merged	O
into	O
the	O
master	B-General_Concept
branch	I-General_Concept
and	O
will	O
be	O
released	O
in	O
the	O
next	O
version	O
.	O
</s>
<s>
File	O
transfer	O
is	O
carried	O
on	O
using	O
a	O
multi-hop	O
swarming	O
system	O
(	O
inspired	O
by	O
the	O
"	O
Turtle	O
Hopping	O
"	O
feature	O
from	O
the	O
Turtle	B-Application
F2F	I-Application
project	O
,	O
but	O
implemented	O
differently	O
)	O
.	O
</s>
<s>
Files	O
are	O
represented	O
by	O
their	O
SHA-1	B-Algorithm
hash	I-Algorithm
value	O
,	O
and	O
HTTP-compliant	O
file	O
and	O
links	O
may	O
be	O
exported	O
,	O
copied	O
,	O
and	O
pasted	O
into/out	O
of	O
Retroshare	B-Application
to	O
publish	O
their	O
virtual	O
location	O
into	O
the	O
Retroshare	B-Application
network	O
.	O
</s>
<s>
Retroshare	B-Application
offers	O
the	O
following	O
services	O
for	O
communication	O
:	O
</s>
<s>
a	O
private	O
chat	B-Protocol
;	O
</s>
<s>
public	O
and	O
private	O
multi-user	O
chat	B-Protocol
lobbies	O
;	O
</s>
<s>
a	O
forum	B-Application
system	O
allowing	O
both	O
anonymous	O
and	O
authenticated	O
forums	O
,	O
which	O
distributes	O
posts	O
from	O
friends	O
to	O
friends	O
;	O
</s>
<s>
VoIP	B-Application
calls	I-Application
;	O
</s>
<s>
Video	B-Application
calls	I-Application
(	O
since	O
version	O
0.6.0	O
)	O
;	O
</s>
<s>
Tor	B-Application
and	O
I2P	B-Protocol
networks	O
support	O
,	O
for	O
further	O
anonymisation	O
(	O
since	O
version	O
0.6.0	O
)	O
.	O
</s>
<s>
The	O
core	O
of	O
the	O
Retroshare	B-Application
software	O
is	O
based	O
on	O
an	O
offline	O
library	O
,	O
into	O
which	O
two	O
executables	O
are	O
plugged	O
:	O
</s>
<s>
a	O
graphical	B-Application
user	I-Application
interface	I-Application
written	O
in	O
Qt	B-Language
is	O
the	O
one	O
most	O
users	O
use	O
.	O
</s>
<s>
In	O
addition	O
to	O
functions	O
quite	O
common	O
to	O
other	O
file-sharing	O
software	O
,	O
such	O
as	O
a	O
search	O
tab	O
and	O
visualization	O
of	O
transfers	O
,	O
Retroshare	B-Application
gives	O
users	O
the	O
potential	O
to	O
manage	O
their	O
network	O
by	O
collecting	O
optional	O
information	O
about	O
neighbouring	O
friends	O
and	O
visualizing	O
it	O
as	O
a	O
trust	O
matrix	O
or	O
as	O
a	O
dynamic	O
network	O
graph	O
.	O
</s>
<s>
The	O
friend-to-friend	O
structure	O
of	O
the	O
Retroshare	B-Application
network	O
makes	O
it	O
difficult	O
to	O
intrude	O
and	O
hardly	O
possible	O
to	O
monitor	O
from	O
an	O
external	O
point	O
of	O
view	O
.	O
</s>
<s>
The	O
degree	O
of	O
anonymity	O
may	O
be	O
improved	O
further	O
by	O
deactivating	O
the	O
DHT	B-Operating_System
and	O
IP/certificate	O
exchange	O
services	O
,	O
making	O
the	O
Retroshare	B-Application
network	O
a	O
real	O
dark	O
net	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
remember	O
that	O
while	O
Retroshare	B-Application
's	O
encryption	O
makes	O
it	O
virtually	O
impossible	O
for	O
an	O
ISP	O
or	O
another	O
external	O
observer	O
to	O
know	O
what	O
one	O
is	O
downloading	O
or	O
uploading	O
,	O
this	O
limitation	O
does	O
not	O
apply	O
to	O
members	O
of	O
the	O
user	O
's	O
Retroshare	B-Application
circle	O
of	O
trust	O
;	O
adding	O
untrusted	O
people	O
to	O
it	O
may	O
be	O
a	O
potential	O
risk	O
.	O
</s>
<s>
In	O
2012	O
,	O
a	O
German	O
Court	O
granted	O
an	O
injunction	O
against	O
a	O
user	O
of	O
Retroshare	B-Application
for	O
sharing	O
copyrighted	O
music	O
files	O
.	O
</s>
<s>
Retroshare	B-Application
derives	O
its	O
security	O
from	O
the	O
fact	O
that	O
all	O
transfers	O
should	O
go	O
through	O
“	O
trusted	O
friends	O
”	O
whom	O
users	O
add	O
.	O
</s>
