<s>
Magnet	O
is	O
a	O
URI	B-Protocol
scheme	I-Protocol
that	O
defines	O
the	O
format	O
of	O
magnet	B-Protocol
links	I-Protocol
,	O
a	O
de	O
facto	O
standard	O
for	O
identifying	O
files	O
(	O
URN	B-Protocol
)	O
by	O
their	O
content	O
,	O
via	O
cryptographic	B-Algorithm
hash	I-Algorithm
value	I-Algorithm
rather	O
than	O
by	O
their	O
location	O
.	O
</s>
<s>
Although	O
magnet	B-Protocol
links	I-Protocol
can	O
be	O
used	O
in	O
a	O
number	O
of	O
contexts	O
,	O
they	O
are	O
particularly	O
useful	O
in	O
peer-to-peer	O
file	O
sharing	O
networks	O
because	O
they	O
allow	O
resources	O
to	O
be	O
referred	O
to	O
without	O
the	O
need	O
for	O
a	O
continuously	O
available	O
host	O
,	O
and	O
can	O
be	O
generated	O
by	O
anyone	O
who	O
already	O
has	O
the	O
file	O
,	O
without	O
the	O
need	O
for	O
a	O
central	O
authority	O
to	O
issue	O
them	O
.	O
</s>
<s>
This	O
makes	O
them	O
popular	O
for	O
use	O
as	O
"	O
guaranteed	O
"	O
search	O
terms	O
within	O
the	O
file	O
sharing	O
community	O
where	O
anyone	O
can	O
distribute	O
a	O
magnet	B-Protocol
link	I-Protocol
to	O
ensure	O
that	O
the	O
resource	O
retrieved	O
by	O
that	O
link	O
is	O
the	O
one	O
intended	O
,	O
regardless	O
of	O
how	O
it	O
is	O
retrieved	O
.	O
</s>
<s>
The	O
standard	O
for	O
Magnet	B-Protocol
URIs	I-Protocol
was	O
developed	O
by	O
Bitzi	O
in	O
2002	O
,	O
partly	O
as	O
a	O
"	O
vendor	O
-	O
and	O
project-neutral	O
generalization	O
"	O
of	O
the	O
ed2k	B-Protocol
:	O
and	O
freenet	B-Protocol
:	O
URI	B-Protocol
schemes	O
used	O
by	O
eDonkey2000	B-Protocol
and	O
Freenet	B-Protocol
,	O
respectively	O
,	O
and	O
attempts	O
to	O
follow	O
official	O
IETF	O
URI	B-Protocol
standards	O
as	O
closely	O
as	O
possible	O
.	O
</s>
<s>
BitTorrent	B-Protocol
introduced	O
the	O
btmh	O
:	O
protocol	O
in	O
2020	O
as	O
part	O
of	O
its	O
BitTorrent	B-Protocol
v2	I-Protocol
changes	O
.	O
</s>
<s>
Magnet	B-Protocol
URIs	I-Protocol
consist	O
of	O
a	O
series	O
of	O
one	O
or	O
more	O
parameters	O
,	O
the	O
order	O
of	O
which	O
is	O
not	O
significant	O
,	O
formatted	O
in	O
the	O
same	O
way	O
as	O
query	B-Protocol
strings	I-Protocol
that	O
ordinarily	O
terminate	O
HTTP	B-Protocol
URLs	O
.	O
</s>
<s>
ParameterNameDescriptionxtExact	O
TopicURN	O
containing	O
file	O
hash	B-Error_Name
.	O
</s>
<s>
This	O
is	O
the	O
most	O
crucial	O
part	O
of	O
the	O
magnet	B-Protocol
link	I-Protocol
,	O
and	O
is	O
used	O
to	O
find	O
and	O
verify	O
the	O
specified	O
file	O
.	O
</s>
<s>
xt	O
=	O
urn:btih:c12fe1c06bba254a9dc9f519b335aa7c1367a88adnDisplay	O
NameA	O
filename	O
to	O
display	O
to	O
the	O
user	O
,	O
for	O
convenience.xleXact	O
LengthThe	O
file	O
size	O
,	O
in	O
bytestrAddress	O
TRackerTracker	O
URL	O
;	O
used	O
to	O
obtain	O
resources	O
for	O
BitTorrent	B-Protocol
downloads	O
without	O
a	O
need	O
for	O
DHT	B-Protocol
support	O
.	O
</s>
<s>
tr	O
=	O
http%3A%2F%	O
2Fexample.org%2FannouncewsWeb	O
SeedThe	O
payload	O
data	O
served	O
over	O
HTTP(S )	O
asAcceptable	O
SourceRefers	O
to	O
a	O
direct	O
download	O
from	O
a	O
web	O
server	O
.	O
</s>
<s>
as	O
=[	O
web	O
link	O
to	O
file(URL encoded )	O
]	O
xseXact	O
SourceEither	O
an	O
HTTP	B-Protocol
(	O
or	O
HTTPS	B-Protocol
,	O
FTP	O
,	O
FTPS	O
,	O
etc	O
.	O
)	O
</s>
<s>
download	O
source	O
for	O
the	O
file	O
pointed	O
to	O
by	O
the	O
Magnet	B-Protocol
link	I-Protocol
,	O
the	O
address	O
of	O
a	O
P2P	O
source	O
for	O
the	O
file	O
or	O
the	O
address	O
of	O
a	O
hub	O
(	O
in	O
the	O
case	O
of	O
DC++	B-Language
)	O
,	O
by	O
which	O
a	O
client	O
tries	O
to	O
connect	O
directly	O
,	O
asking	O
for	O
the	O
file	O
and/or	O
its	O
sources	O
.	O
</s>
<s>
This	O
field	O
is	O
commonly	O
used	O
by	O
P2P	O
clients	O
to	O
store	O
the	O
source	O
,	O
and	O
may	O
include	O
the	O
file	O
hash	B-Error_Name
.	O
</s>
<s>
</s>
<s>
mt	O
=	O
urn:sha1:3I42H3S6NNFQ2MSVX7XZKYAYSCX5QBYJsoSelect	O
OnlyLists	O
specific	O
files	O
torrent	B-Protocol
clients	O
should	O
download	O
,	O
indicated	O
as	O
individual	O
or	O
ranges	O
(	O
inclusive	O
)	O
of	O
file	O
indexes	O
.	O
</s>
<s>
trackers	B-Protocol
or	O
DHT	B-Protocol
.	O
</s>
<s>
The	O
xt	O
parameter	O
specifies	O
the	O
URN	B-Protocol
for	O
a	O
given	O
p2p	O
protocol	O
.	O
</s>
<s>
Its	O
purpose	O
is	O
to	O
provide	O
a	O
search	O
parameter	O
for	O
finding	O
the	O
metadata	O
to	O
the	O
torrent	B-Protocol
.	O
</s>
<s>
This	O
effectively	O
acts	O
as	O
a	O
replacement	O
to	O
a	O
.torrent	O
file	O
,	O
which	O
itself	O
contains	O
the	O
torrent	B-Protocol
metadata	O
,	O
by	O
instead	O
searching	O
the	O
p2p	O
network	O
(	O
using	O
the	O
URN	B-Protocol
)	O
for	O
that	O
metadata	O
.	O
</s>
<s>
Each	O
protocol	O
handles	O
a	O
URN	B-Protocol
uniquely	O
;	O
for	O
example	O
,	O
xt	O
=	O
urn:btih:FFC7E738EAA4CD4ECF51EC6FD669C6CDE2C281A8	O
uses	O
the	O
btih	O
(	O
BitTorrent	B-Protocol
v1	O
protocol	O
)	O
,	O
so	O
a	O
BitTorrent	B-Protocol
client	O
can	O
take	O
the	O
hash	B-Error_Name
and	O
lookup	O
the	O
torrent	B-Protocol
's	O
metadata	O
in	O
the	O
BitTorrent	B-Protocol
DHT	I-Protocol
.	O
</s>
<s>
In	O
the	O
case	O
of	O
DHT	B-Protocol
the	O
client	O
searches	O
through	O
a	O
set	O
of	O
pre-known	O
nodes	O
and	O
requests	O
the	O
metadata	O
for	O
an	O
infohash	O
;	O
those	O
nodes	O
will	O
make	O
the	O
same	O
request	O
to	O
other	O
known	O
nodes	O
until	O
eventually	O
a	O
swarm	O
is	O
found	O
and	O
returned	O
.	O
</s>
<s>
Tiger	O
Tree	O
Hash	B-Error_Name
(	O
TTH	O
)	O
These	O
hashes	B-Error_Name
are	O
used	O
on	O
Direct	O
Connect	O
and	O
G2	O
(	O
Gnutella2	O
)	O
,	O
among	O
others	O
.	O
</s>
<s>
Secure	B-Algorithm
Hash	I-Algorithm
Algorithm	I-Algorithm
1	I-Algorithm
(	O
SHA-1	B-Algorithm
)	O
These	O
hash	B-Error_Name
sums	I-Error_Name
are	O
used	O
on	O
gnutella	B-Protocol
and	O
G2	O
(	O
Gnutella2	O
)	O
.	O
</s>
<s>
BitPrint	O
Such	O
hash	B-Error_Name
sums	I-Error_Name
consist	O
of	O
an	O
SHA-1	B-Algorithm
Hash	I-Algorithm
,	O
followed	O
by	O
a	O
TTH	O
Hash	B-Error_Name
,	O
delimited	O
by	O
a	O
point	O
;	O
they	O
are	O
used	O
on	O
gnutella	B-Protocol
and	O
G2	O
(	O
Gnutella2	O
)	O
.	O
</s>
<s>
xt	O
=	O
urn:bitprint:	O
[	O
SHA-1	B-Algorithm
Hash	I-Algorithm
(	O
Base32	O
)	O
]	O
.	O
</s>
<s>
ED2K	B-Protocol
(	O
eDonkey2000	B-Protocol
)	O
hash	B-Error_Name
These	O
hash	B-Error_Name
sums	I-Error_Name
are	O
used	O
on	O
eDonkey2000	B-Protocol
.	O
</s>
<s>
Advanced	O
Intelligent	O
Corruption	O
Handler	O
(	O
AICH	O
)	O
Not	O
formal	O
URNs	B-Protocol
for	O
Magnet	B-Protocol
links	I-Protocol
,	O
such	O
hash	B-Error_Name
sums	I-Error_Name
are	O
used	O
by	O
eDonkey2000	B-Protocol
to	O
restore	O
and	O
control	O
the	O
integrity	O
of	O
downloading	O
and	O
already	O
downloaded	O
files	O
.	O
</s>
<s>
Kazaa	B-Protocol
hash	B-Error_Name
Used	O
on	O
FastTrack	B-Protocol
,	O
these	O
hash	B-Error_Name
sums	I-Error_Name
are	O
vulnerable	O
to	O
hash	B-Algorithm
collision	I-Algorithm
attacks	I-Algorithm
.	O
</s>
<s>
BitTorrent	B-Protocol
info	O
hash	B-Error_Name
(	O
BTIH	O
)	O
These	O
are	O
hex-encoded	O
SHA-1	B-Algorithm
hash	I-Algorithm
sums	O
of	O
the	O
"	O
info	O
"	O
sections	O
of	O
BitTorrent	B-Protocol
metafiles	O
as	O
used	O
by	O
BitTorrent	B-Protocol
to	O
identify	O
downloadable	O
files	O
or	O
sets	O
of	O
files	O
.	O
</s>
<s>
For	O
backwards	O
compatibility	O
with	O
existing	O
links	O
,	O
clients	O
should	O
also	O
support	O
the	O
Base32	O
encoded	O
version	O
of	O
the	O
hash	B-Error_Name
.	O
</s>
<s>
Some	O
clients	O
require	O
Base32	O
of	O
info_hash	O
(	O
e.g.	O
,	O
Vuze	B-Application
)	O
.	O
</s>
<s>
BitTorrent	B-Protocol
info	O
hash	B-Error_Name
v2	O
(	O
BTMH	O
)	O
BitTorrent	B-Protocol
v2	I-Protocol
replaces	O
the	O
obsolete	B-Algorithm
SHA-1	I-Algorithm
hash	I-Algorithm
with	O
a	O
SHA-256	B-Algorithm
info	O
hash	B-Error_Name
.	O
</s>
<s>
Message	B-Algorithm
Digest	I-Algorithm
5	I-Algorithm
(	O
MD5	B-Algorithm
)	O
Supported	O
by	O
G2	O
(	O
Gnutella2	O
)	O
,	O
such	O
hashes	B-Error_Name
are	O
vulnerable	O
to	O
hash	B-Algorithm
collision	I-Algorithm
attacks	I-Algorithm
.	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
download	O
links	O
that	O
a	O
Magnet	B-Protocol
link	I-Protocol
can	O
include	O
as	O
a	O
direct	O
or	O
backup	O
source	O
.	O
</s>
<s>
Content-Addressable	O
Web	O
URL	O
This	O
type	O
of	O
-based	O
link	O
is	O
used	O
by	O
gnutella	B-Protocol
as	O
well	O
as	O
G2	O
applications	O
.	O
</s>
<s>
</s>
<s>
This	O
system	O
operates	O
similar	O
to	O
a	O
BitTorrent	B-Protocol
tracker	I-Protocol
.	O
</s>
