<s>
GNUnet	B-Language
is	O
a	O
software	B-Architecture
framework	I-Architecture
for	O
decentralized	O
,	O
peer-to-peer	O
networking	B-Architecture
and	O
an	O
official	O
GNU	B-Application
package	O
.	O
</s>
<s>
The	O
framework	O
offers	O
link	B-General_Concept
encryption	I-General_Concept
,	O
peer	B-Protocol
discovery	I-Protocol
,	O
resource	B-Algorithm
allocation	I-Algorithm
,	O
communication	O
over	O
many	O
transports	O
(	O
such	O
as	O
TCP	B-Protocol
,	O
UDP	B-Protocol
,	O
HTTP	B-Protocol
,	O
HTTPS	B-Protocol
,	O
WLAN	B-Architecture
and	O
Bluetooth	B-Protocol
)	O
and	O
various	O
basic	O
peer-to-peer	O
algorithms	O
for	O
routing	B-Protocol
,	O
multicast	O
and	O
network	O
size	O
estimation	O
.	O
</s>
<s>
GNUnet	B-Language
's	O
basic	O
network	O
topology	O
is	O
that	O
of	O
a	O
mesh	B-Architecture
network	I-Architecture
.	O
</s>
<s>
GNUnet	B-Language
includes	O
a	O
distributed	B-Operating_System
hash	I-Operating_System
table	I-Operating_System
(	O
DHT	O
)	O
which	O
is	O
a	O
randomized	O
variant	O
of	O
Kademlia	B-Operating_System
that	O
can	O
still	O
efficiently	O
route	O
in	O
small-world	O
networks	O
.	O
</s>
<s>
GNUnet	B-Language
offers	O
a	O
"	O
F2F	O
topology	O
"	O
option	O
for	O
restricting	O
connections	O
to	O
only	O
the	O
users	O
 '	O
trusted	O
friends	O
.	O
</s>
<s>
GNUnet	B-Language
uses	O
Uniform	B-Protocol
resource	I-Protocol
identifiers	I-Protocol
(	O
not	O
approved	O
by	O
IANA	O
,	O
although	O
an	O
application	O
has	O
been	O
made	O
)	O
.	O
</s>
<s>
GNUnet	B-Language
URIs	B-Protocol
consist	O
of	O
two	O
major	O
parts	O
:	O
the	O
module	O
and	O
the	O
module	O
specific	O
identifier	O
.	O
</s>
<s>
A	O
GNUnet	B-Language
URI	B-Protocol
is	O
of	O
form	O
gnunet://module/identifier	O
where	O
module	O
is	O
the	O
module	O
name	O
and	O
identifier	O
is	O
a	O
module	O
specific	O
string	O
.	O
</s>
<s>
The	O
primary	O
codebase	O
is	O
written	O
in	O
C	B-Language
,	O
but	O
there	O
are	O
bindings	O
in	O
other	O
languages	O
to	O
produce	O
an	O
API	O
for	O
developing	O
extensions	O
in	O
those	O
languages	O
.	O
</s>
<s>
GNUnet	B-Language
is	O
part	O
of	O
the	B-Application
GNU	I-Application
Project	I-Application
.	O
</s>
<s>
GNUnet	B-Language
consists	O
of	O
several	O
subsystems	O
,	O
of	O
which	O
essential	O
ones	O
are	O
Transport	O
and	O
Core	O
subsystems	O
.	O
</s>
<s>
Transport	O
subsystem	O
provides	O
insecure	O
link-layer	O
communications	O
,	O
while	O
Core	O
provides	O
peer	B-Protocol
discovery	I-Protocol
and	O
encryption	O
.	O
</s>
<s>
GNUnet	B-Language
includes	O
various	O
P2P	O
applications	O
in	O
the	O
main	O
distribution	O
of	O
the	O
framework	O
,	O
including	O
filesharing	O
,	O
chat	O
and	O
VPN	O
;	O
additionally	O
,	O
a	O
few	O
external	O
projects	O
(	O
such	O
as	O
secushare	O
)	O
are	O
also	O
extending	O
the	O
GNUnet	B-Language
infrastructure	O
.	O
</s>
<s>
GNUnet	B-Language
is	O
unrelated	O
to	O
the	O
older	O
Gnutella	B-Protocol
P2P	O
protocol	O
.	O
</s>
<s>
Gnutella	B-Protocol
is	O
not	O
an	O
official	O
GNU	B-Application
project	I-Application
,	O
while	O
GNUnet	B-Language
is	O
.	O
</s>
<s>
Originally	O
,	O
GNUnet	B-Language
used	O
UDP	B-Protocol
for	O
underlying	O
transport	O
.	O
</s>
<s>
Now	O
GNUnet	B-Language
transport	O
subsystem	O
provides	O
multiple	O
options	O
,	O
such	O
as	O
TCP	B-Protocol
and	O
SMTP	O
.	O
</s>
<s>
The	O
communication	O
port	O
,	O
officially	O
registered	O
at	O
IANA	O
,	O
is	O
2086	O
(	O
tcp	B-Protocol
+	O
udp	B-Protocol
)	O
.	O
</s>
<s>
GNUnet	B-Language
provides	O
trust	O
system	O
based	O
on	O
excess-based	O
economic	O
model	O
.	O
</s>
<s>
GNUnet	B-Language
network	O
has	O
no	O
trusted	O
entities	O
so	O
it	O
is	O
impossible	O
to	O
maintain	O
global	O
reputation	O
.	O
</s>
<s>
The	O
primary	O
application	O
at	O
this	O
point	O
is	O
anonymous	O
,	O
censorship-resistant	O
file-sharing	O
,	O
allowing	O
users	O
to	O
anonymously	O
publish	O
or	O
retrieve	O
information	O
of	O
all	O
kinds	O
.	O
</s>
<s>
The	O
GNUnet	B-Language
protocol	O
which	O
provides	O
anonymity	O
is	O
called	O
GAP	O
(	O
GNUnet	B-Language
anonymity	O
protocol	O
)	O
.	O
</s>
<s>
GNUnet	B-Language
FS	O
can	O
additionally	O
make	O
use	O
of	O
GNU	B-Application
libextractor	O
to	O
automatically	O
annotate	O
shared	O
files	O
with	O
metadata	O
.	O
</s>
<s>
Files	O
shared	O
with	O
GNUnet	B-Language
are	O
ECRS	O
(	O
An	O
Encoding	O
for	O
Censorship-Resistant	O
Sharing	O
)	O
coded	O
.	O
</s>
<s>
DBlocks	O
are	O
linked	O
together	O
into	O
Merkle	B-Algorithm
tree	I-Algorithm
by	O
means	O
of	O
IBlocks	O
that	O
store	O
DBlock	O
identifiers	O
.	O
</s>
<s>
GNUnet	B-Language
Anonymity	O
Protocol	O
consists	O
of	O
queries	O
and	O
replies	O
.	O
</s>
<s>
Reply	O
address	O
is	O
the	O
major	O
difference	O
compared	O
to	O
Freenet	B-Protocol
protocol	O
.	O
</s>
<s>
While	O
in	O
Freenet	B-Protocol
reply	O
always	O
propagates	O
back	O
using	O
the	O
same	O
path	O
as	O
the	O
query	O
,	O
in	O
GNUnet	B-Language
the	O
path	O
may	O
be	O
shorter	O
.	O
</s>
<s>
GNUnet	B-Language
's	O
DHT	O
infrastructure	O
is	O
only	O
used	O
if	O
non-anonymous	O
file-sharing	O
is	O
specified	O
.	O
</s>
<s>
Most	O
URIs	B-Protocol
contain	O
hashes	O
,	O
which	O
are	O
encoded	O
in	O
base32hex	O
.	O
</s>
<s>
chk	O
identifies	O
files	O
,	O
typically	O
:	O
gnunet://fs/chk/	O
[ file	O
hash ]	O
.	O
</s>
<s>
A	O
type	O
of	O
GNUnet	B-Language
filesharing	O
URI	B-Protocol
pointing	O
to	O
a	O
specific	O
copy	O
of	O
GNU	B-License
GPL	I-License
license	I-License
text	O
:	O
</s>
<s>
Another	O
type	O
of	O
GNUnet	B-Language
filesharing	O
URI	B-Protocol
,	O
pointing	O
to	O
the	O
search	O
results	O
of	O
a	O
search	O
with	O
keyword	O
"	O
gpl	B-License
"	O
:	O
</s>
<s>
GNUnet	B-Language
includes	O
an	O
implementation	O
of	O
the	O
GNU	B-Application
Name	O
System	O
(	O
GNS	O
)	O
,	O
a	O
decentralized	O
and	O
censorship-resistant	O
replacement	O
for	O
DNS	B-Protocol
.	O
</s>
<s>
In	O
GNS	O
,	O
each	O
user	O
manages	O
their	O
own	O
zones	B-Protocol
and	O
can	O
delegate	O
subdomains	O
to	O
zones	B-Protocol
managed	O
by	O
other	O
users	O
.	O
</s>
<s>
Lookups	O
of	O
records	O
defined	O
by	O
other	O
users	O
are	O
performed	O
using	O
GNUnet	B-Language
's	O
DHT	O
.	O
</s>
<s>
GNUnet	B-Language
can	O
tunnel	O
IP	O
traffic	O
over	O
the	O
peer-to-peer	O
network	O
.	O
</s>
<s>
If	O
necessary	O
,	O
GNUnet	B-Language
can	O
perform	O
IPv4-IPv6	O
protocol	B-Protocol
translation	I-Protocol
in	O
the	O
process	O
.	O
</s>
<s>
GNUnet	B-Language
provides	O
a	O
DNS	B-Protocol
Application-level	O
gateway	O
to	O
proxy	O
DNS	B-Protocol
requests	O
and	O
map	O
addresses	O
to	O
the	O
desired	O
address	O
family	O
as	O
necessary	O
.	O
</s>
<s>
This	O
way	O
,	O
GNUnet	B-Language
offers	O
a	O
possible	O
technology	O
to	O
facilitate	O
IPv6	B-Protocol
transition	I-Protocol
.	O
</s>
<s>
Furthermore	O
,	O
in	O
combination	O
with	O
GNS	O
,	O
GNUnet	B-Language
's	O
protocol	B-Protocol
translation	I-Protocol
system	O
can	O
be	O
used	O
to	O
access	O
hidden	O
services	O
—	O
IP-based	O
services	O
that	O
run	O
locally	O
at	O
some	O
peer	O
in	O
the	O
network	O
and	O
which	O
can	O
only	O
be	O
accessed	O
by	O
resolving	O
a	O
GNS	O
name	O
.	O
</s>
<s>
Gabor	O
X	O
Toth	O
published	O
in	O
early	O
September	O
2013	O
a	O
thesis	O
to	O
present	O
the	O
design	O
of	O
a	O
social	B-Application
messaging	I-Application
service	O
for	O
the	O
GNUnet	B-Language
peer-to-peer	O
framework	O
that	O
offers	O
scalability	O
,	O
extensibility	O
,	O
and	O
end-to-end	O
encrypted	O
communication	O
.	O
</s>
<s>
The	O
scalability	O
property	O
is	O
achieved	O
through	O
multicast	O
message	O
delivery	O
,	O
while	O
extensibility	O
is	O
made	O
possible	O
by	O
using	O
PSYC	O
(	O
Protocol	O
for	O
SYnchronous	B-Protocol
Conferencing	I-Protocol
)	O
,	O
which	O
provides	O
an	O
extensible	O
RPC	B-Operating_System
(	O
Remote	B-Operating_System
Procedure	I-Operating_System
Call	I-Operating_System
)	O
syntax	O
that	O
can	O
evolve	O
over	O
time	O
without	O
having	O
to	O
upgrade	O
the	O
software	O
on	O
all	O
nodes	O
in	O
the	O
network	O
.	O
</s>
<s>
End-to-end	O
encrypted	O
communication	O
is	O
provided	O
by	O
the	O
mesh	O
service	O
of	O
GNUnet	B-Language
,	O
upon	O
which	O
the	O
multicast	O
channels	O
are	O
built	O
.	O
</s>
<s>
Pseudonymous	O
users	O
and	O
social	O
places	O
in	O
the	O
system	O
have	O
cryptographical	O
identities	O
—	O
identified	O
by	O
their	O
public	O
key	O
—	O
these	O
are	O
mapped	O
to	O
human	O
memorable	O
names	O
using	O
GNS	O
(	O
GNU	B-Application
Name	O
System	O
)	O
,	O
where	O
each	O
pseudonym	O
has	O
a	O
zone	O
pointing	O
to	O
its	O
places	O
.	O
</s>
<s>
That	O
is	O
the	O
required	O
building	O
block	O
for	O
turning	O
the	O
GNUnet	B-Language
framework	O
into	O
a	O
fully	O
peer-to-peer	O
social	O
networking	B-Architecture
platform	O
.	O
</s>
<s>
A	O
chat	O
has	O
been	O
implemented	O
in	O
the	O
CADET	O
module	O
,	O
for	O
which	O
a	O
GTK	B-Application
interface	O
for	O
GNOME	B-Application
exists	O
,	O
specifically	O
designed	O
for	O
the	O
emerging	O
Linux	B-Application
phones	O
(	O
such	O
as	O
the	O
Librem	B-Application
5	I-Application
or	O
the	O
PinePhone	B-Application
)	O
.	O
</s>
