<s>
In	O
computing	O
,	O
eD2k	B-Protocol
links	I-Protocol
(	O
ed2k://	B-Protocol
)	O
are	O
hyperlinks	O
used	O
to	O
denote	O
files	O
stored	O
on	O
computers	O
connected	O
to	O
the	O
eDonkey	O
filesharing	O
P2P	O
network	O
.	O
</s>
<s>
Many	O
programs	O
,	O
such	O
as	O
eMule	B-Protocol
,	O
MLDonkey	B-Protocol
and	O
the	O
original	O
eDonkey2000	B-Protocol
client	O
by	O
MetaMachine	O
,	O
which	O
introduced	O
the	O
link	O
type	O
,	O
as	O
well	O
as	O
others	O
using	O
the	O
eDonkey	O
file	O
sharing	O
protocol	O
,	O
can	O
be	O
used	O
to	O
manage	O
files	O
stored	O
in	O
the	O
filesharing	O
network	O
.	O
</s>
<s>
eD2k	B-Protocol
links	I-Protocol
allow	O
a	O
file	O
to	O
be	O
identified	O
from	O
a	O
link	O
in	O
a	O
web	O
browser	O
and	O
to	O
be	O
downloaded	O
thereafter	O
by	O
a	O
client	O
like	O
eMule	B-Protocol
,	O
Shareaza	B-Application
or	O
any	O
other	O
compatible	O
software	O
.	O
</s>
<s>
This	O
linking	O
feature	O
was	O
one	O
of	O
the	O
first	O
URIs	B-Protocol
to	O
be	O
introduced	O
in	O
peer-to-peer	O
file	O
sharing	O
,	O
and	O
had	O
a	O
vast	O
effect	O
on	O
the	O
development	O
of	O
the	O
eDonkey	O
network	O
,	O
as	O
it	O
allowed	O
external	O
link	O
sites	O
to	O
provide	O
verified	O
content	O
within	O
the	O
network	O
.	O
</s>
<s>
Nowadays	O
,	O
so-called	O
Magnet	B-Protocol
links	I-Protocol
have	O
replaced	O
eD2k	B-Protocol
links	I-Protocol
in	O
practice	O
.	O
</s>
<s>
They	O
serve	O
a	O
similar	O
role	O
,	O
but	O
are	O
not	O
limited	O
to	O
the	O
eD2k	B-Protocol
hash	B-Error_Name
and	O
can	O
contain	O
other	O
hashes	B-Error_Name
such	O
as	O
SHA-1	B-Algorithm
or	O
MD5	B-Algorithm
for	O
example	O
,	O
which	O
makes	O
it	O
possible	O
to	O
use	O
these	O
links	O
to	O
point	O
to	O
files	O
in	O
several	O
networks	O
(	O
as	O
well	O
as	O
in	O
BitTorrent	O
)	O
at	O
once	O
.	O
</s>
<s>
eD2k	B-Protocol
links	I-Protocol
include	O
file	O
hashes	B-Error_Name
,	O
as	O
these	O
hashes	B-Error_Name
can	O
be	O
used	O
as	O
a	O
unique	O
identifier	O
for	O
files	O
within	O
the	O
network	O
,	O
so	O
even	O
if	O
the	O
linked-to	O
file	O
has	O
a	O
different	O
name	O
on	O
two	O
computers	O
within	O
the	O
network	O
,	O
the	O
file	O
can	O
be	O
found	O
on	O
both	O
of	O
them	O
,	O
and	O
file	O
chunks	O
can	O
be	O
obtained	O
from	O
both	O
sources	O
.	O
</s>
<s>
This	O
is	O
done	O
by	O
using	O
a	O
hash	B-Error_Name
function	I-Error_Name
on	O
the	O
file	O
to	O
calculate	O
its	O
checksum	O
,	O
depending	O
only	O
from	O
the	O
file	O
content	O
,	O
not	O
from	O
its	O
name	O
.	O
</s>
<s>
Like	O
other	O
URI	B-Protocol
protocols	O
,	O
web	O
browsers	O
can	O
be	O
configured	O
to	O
automatically	O
handle	O
ed2k	B-Protocol
URIs	I-Protocol
.	O
</s>
<s>
After	O
installing	O
an	O
eD2k	B-Protocol
client	I-Protocol
,	O
the	O
eD2k	B-Protocol
protocol	O
is	O
optionally	O
registered	O
so	O
that	O
clicking	O
on	O
it	O
in	O
the	O
browser	O
automatically	O
starts	O
the	O
download	O
or	O
asks	O
whether	O
the	O
user	O
wants	O
to	O
start	O
downloading	O
.	O
</s>
<s>
The	O
typical	O
eD2k	B-Protocol
file	O
link	O
also	O
includes	O
the	O
filename	B-Device
and	O
the	O
file	O
size	O
.	O
</s>
<s>
eD2k	B-Protocol
links	I-Protocol
can	O
also	O
include	O
a	O
reference	O
to	O
the	O
IP	B-Protocol
address	I-Protocol
and	O
port	O
of	O
specific	O
clients	O
that	O
are	O
known	O
to	O
share	O
the	O
linked-to	O
file	O
.	O
</s>
<s>
On	O
eMule	B-Protocol
,	O
the	O
link	O
often	O
contains	O
also	O
an	O
AICH	O
top	B-Algorithm
hash	I-Algorithm
|h	O
=	O
H52BRVWPBBTAED5NXQDH2RJDDAKRUWST|	O
to	O
help	O
recover	O
the	O
file	O
in	O
case	O
of	O
corruption	O
during	O
file	O
transfer	O
.	O
</s>
<s>
The	O
eD2k	B-Protocol
hash	B-Error_Name
function	I-Error_Name
is	O
a	O
root	B-Algorithm
hash	I-Algorithm
of	O
a	O
list	O
of	O
MD4	B-Algorithm
hashes	I-Algorithm
.	O
</s>
<s>
It	O
gives	O
a	O
different	O
result	O
than	O
a	O
simple	O
usage	O
of	O
the	O
MD4	B-Algorithm
algorithm	O
.	O
</s>
<s>
The	O
file	O
data	O
is	O
divided	O
into	O
full	O
chunks	O
of	O
9500	O
KiB	O
(	O
9728000	O
bytes	O
)	O
plus	O
a	O
remainder	O
chunk	O
,	O
and	O
a	O
separate	O
128-bit	O
MD4	B-Algorithm
checksum	O
is	O
computed	O
for	O
each	O
.	O
</s>
<s>
If	O
the	O
file	O
is	O
greater	O
than	O
9500	O
KiB	O
(	O
which	O
means	O
that	O
there	O
is	O
more	O
than	O
one	O
chunk	O
)	O
,	O
the	O
eD2k	B-Protocol
hash	B-Error_Name
is	O
computed	O
by	O
concatenating	O
the	O
chunks	O
 '	O
MD4	B-Algorithm
checksums	O
in	O
order	O
and	O
hashing	O
the	O
result	O
again	O
using	O
MD4	B-Algorithm
.	O
</s>
<s>
Otherwise	O
,	O
the	O
MD4	B-Algorithm
hash	I-Algorithm
of	O
the	O
only	O
chunk	O
of	O
the	O
file	O
is	O
used	O
with	O
no	O
further	O
modifications	O
.	O
</s>
<s>
This	O
method	O
of	O
hashing	O
allows	O
the	O
recipient	O
to	O
verify	O
that	O
a	O
hash	B-Algorithm
list	I-Algorithm
corresponds	O
to	O
an	O
original	O
eD2k	B-Protocol
file	O
hash	B-Error_Name
,	O
without	O
the	O
need	O
to	O
actually	O
have	O
the	O
file	O
present	O
on	O
disk	O
.	O
</s>
<s>
Old	O
versions	O
of	O
some	O
eD2k	B-Protocol
hash	B-Error_Name
tools	O
computed	O
file	O
hashes	B-Error_Name
with	O
an	O
additional	O
0-byte	O
chunk	O
at	O
the	O
end	O
.	O
</s>
<s>
This	O
practice	O
is	O
discouraged	O
however	O
and	O
the	O
first	O
interpretation	O
is	O
used	O
as	O
a	O
standard	O
nowadays	O
to	O
prevent	O
some	O
files	O
from	O
having	O
different	O
hashes	B-Error_Name
depending	O
on	O
the	O
algorithm	O
implementation	O
used	O
to	O
calculate	O
their	O
hash	B-Error_Name
.	O
</s>
<s>
The	O
AICH	O
(	O
Advanced	O
Intelligent	O
Corruption	O
Handling	O
)	O
is	O
an	O
emule	B-Protocol
extension	O
.	O
</s>
<s>
It	O
subdivides	O
the	O
9500	O
KiB	O
chunk	O
into	O
180-KiB	O
blocks	O
and	O
builds	O
a	O
merkel	B-Algorithm
tree	I-Algorithm
out	O
of	O
the	O
SHA1	B-Algorithm
hashes	B-Error_Name
of	O
the	O
53	O
blocks	O
,	O
so	O
that	O
the	O
root	B-Algorithm
hash	I-Algorithm
of	O
each	O
block	O
is	O
called	O
a	O
block	O
hash	B-Error_Name
.	O
</s>
<s>
The	O
block	O
hashes	B-Error_Name
further	O
feed	O
into	O
a	O
merkel	B-Algorithm
tree	I-Algorithm
,	O
the	O
root	B-Algorithm
hash	I-Algorithm
of	O
which	O
is	O
the	O
actual	O
AICH	O
root	B-Algorithm
hash	I-Algorithm
.	O
</s>
<s>
The	O
smaller	O
block	O
size	O
allows	O
eMule	B-Protocol
clients	O
to	O
more	O
precisely	O
identifify	O
locations	O
of	O
corruption	O
.	O
</s>
<s>
A	O
server	O
link	O
is	O
a	O
reference	O
to	O
an	O
eDonkey2000	B-Protocol
server	O
;	O
clicking	O
on	O
such	O
a	O
link	O
typically	O
adds	O
it	O
to	O
the	O
server	O
list	O
.	O
</s>
