<s>
Parchive	B-General_Concept
(	O
a	O
portmanteau	O
of	O
parity	B-General_Concept
archive	I-General_Concept
,	O
and	O
formally	O
known	O
as	O
Parity	B-Error_Name
Volume	O
Set	O
Specification	O
)	O
is	O
an	O
erasure	O
code	O
system	O
that	O
produces	O
par	B-General_Concept
files	I-General_Concept
for	O
checksum	B-Algorithm
verification	O
of	O
data	O
integrity	O
,	O
with	O
the	O
capability	O
to	O
perform	O
data	B-Application
recovery	I-Application
operations	O
that	O
can	O
repair	O
or	O
regenerate	O
corrupted	O
or	O
missing	O
data	O
.	O
</s>
<s>
Parchive	B-General_Concept
was	O
originally	O
written	O
to	O
solve	O
the	O
problem	O
of	O
reliable	O
file	O
sharing	O
on	O
Usenet	B-Application
,	O
but	O
it	O
can	O
be	O
used	O
for	O
protecting	O
any	O
kind	O
of	O
data	O
from	O
data	O
corruption	O
,	O
disc	B-Device
rot	I-Device
,	O
bit	O
rot	O
,	O
and	O
accidental	O
or	O
malicious	O
damage	O
.	O
</s>
<s>
Despite	O
the	O
name	O
,	O
Parchive	B-General_Concept
uses	O
more	O
advanced	O
techniques	O
(	O
specifically	O
error	B-Error_Name
correction	I-Error_Name
codes	I-Error_Name
)	O
than	O
simplistic	O
parity	B-Error_Name
methods	O
of	O
error	B-Error_Name
detection	I-Error_Name
.	O
</s>
<s>
As	O
of	O
2014	O
,	O
PAR1	O
is	O
obsolete	O
,	O
PAR2	O
is	O
mature	O
for	O
widespread	O
use	O
,	O
and	O
PAR3	O
is	O
a	O
discontinued	O
experimental	O
version	O
developed	O
by	O
MultiPar	B-General_Concept
author	O
Yutaka	O
Sawada	O
.	O
</s>
<s>
The	O
original	O
SourceForge	O
Parchive	B-General_Concept
project	O
has	O
been	O
inactive	O
since	O
April	O
30	O
,	O
2015	O
.	O
</s>
<s>
Parchive	B-General_Concept
was	O
intended	O
to	O
increase	O
the	O
reliability	O
of	O
transferring	O
files	O
via	O
Usenet	B-Application
newsgroups	I-Application
.	O
</s>
<s>
Usenet	B-Application
was	O
originally	O
designed	O
for	O
informal	O
conversations	O
,	O
and	O
the	O
underlying	O
protocol	O
,	O
NNTP	B-Protocol
was	O
not	O
designed	O
to	O
transmit	O
arbitrary	O
binary	O
data	O
.	O
</s>
<s>
Another	O
limitation	O
,	O
which	O
was	O
acceptable	O
for	O
conversations	O
but	O
not	O
for	O
files	O
,	O
was	O
that	O
messages	O
were	O
normally	O
fairly	O
short	O
in	O
length	O
and	O
limited	O
to	O
7-bit	B-Protocol
ASCII	I-Protocol
text	O
.	O
</s>
<s>
Various	O
techniques	O
were	O
devised	O
to	O
send	O
files	O
over	O
Usenet	B-Application
,	O
such	O
as	O
uuencoding	B-Device
and	O
Base64	B-Protocol
.	O
</s>
<s>
Later	O
Usenet	B-Application
software	O
allowed	O
8	O
bit	O
Extended	B-Protocol
ASCII	I-Protocol
,	O
which	O
permitted	O
new	O
techniques	O
like	O
yEnc	O
.	O
</s>
<s>
Large	O
files	O
were	O
broken	O
up	O
to	O
reduce	O
the	O
effect	O
of	O
a	O
corrupted	O
download	B-Application
,	O
but	O
the	O
unreliable	O
nature	O
of	O
Usenet	B-Application
remained	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
Parchive	B-General_Concept
,	O
parity	B-General_Concept
files	I-General_Concept
could	O
be	O
created	O
that	O
were	O
then	O
uploaded	O
along	O
with	O
the	O
original	O
data	O
files	O
.	O
</s>
<s>
If	O
any	O
of	O
the	O
data	O
files	O
were	O
damaged	O
or	O
lost	O
while	O
being	O
propagated	O
between	O
Usenet	B-Application
servers	O
,	O
users	O
could	O
download	B-Application
parity	B-General_Concept
files	I-General_Concept
and	O
use	O
them	O
to	O
reconstruct	O
the	O
damaged	O
or	O
missing	O
files	O
.	O
</s>
<s>
Parchive	B-General_Concept
included	O
the	O
construction	O
of	O
small	O
index	O
files	O
( *	O
.par	B-General_Concept
in	O
version	O
1	O
and	O
*	O
.par2	B-General_Concept
in	O
version	O
2	O
)	O
that	O
do	O
not	O
contain	O
any	O
recovery	O
data	O
.	O
</s>
<s>
These	O
indexes	O
contain	O
file	O
hashes	B-Error_Name
that	O
can	O
be	O
used	O
to	O
quickly	O
identify	O
the	O
target	O
files	O
and	O
verify	O
their	O
integrity	O
.	O
</s>
<s>
Because	O
the	O
index	O
files	O
were	O
so	O
small	O
,	O
they	O
minimized	O
the	O
amount	O
of	O
extra	O
data	O
that	O
had	O
to	O
be	O
downloaded	B-Application
from	O
Usenet	B-Application
to	O
verify	O
that	O
the	O
data	O
files	O
were	O
all	O
present	O
and	O
undamaged	O
,	O
or	O
to	O
determine	O
how	O
many	O
parity	B-Error_Name
volumes	O
were	O
required	O
to	O
repair	O
any	O
damage	O
or	O
reconstruct	O
any	O
missing	O
files	O
.	O
</s>
<s>
They	O
were	O
most	O
useful	O
in	O
version	O
1	O
where	O
the	O
parity	B-Error_Name
volumes	O
were	O
much	O
larger	O
than	O
the	O
short	O
index	O
files	O
.	O
</s>
<s>
These	O
larger	O
parity	B-Error_Name
volumes	O
contain	O
the	O
actual	O
recovery	O
data	O
along	O
with	O
a	O
duplicate	O
copy	O
of	O
the	O
information	O
in	O
the	O
index	O
files	O
(	O
which	O
allows	O
them	O
to	O
be	O
used	O
on	O
their	O
own	O
to	O
verify	O
the	O
integrity	O
of	O
the	O
data	O
files	O
if	O
there	O
is	O
no	O
small	O
index	O
file	O
available	O
)	O
.	O
</s>
<s>
In	O
July	O
2001	O
,	O
Tobias	O
Rieper	O
and	O
Stefan	O
Wehlus	O
proposed	O
the	O
Parity	B-Error_Name
Volume	O
Set	O
specification	O
,	O
and	O
with	O
the	O
assistance	O
of	O
other	O
project	O
members	O
,	O
version	O
1.0	O
of	O
the	O
specification	O
was	O
published	O
in	O
October	O
2001	O
.	O
</s>
<s>
Par1	O
used	O
Reed	B-Error_Name
–	I-Error_Name
Solomon	I-Error_Name
error	I-Error_Name
correction	I-Error_Name
to	O
create	O
new	O
recovery	O
files	O
.	O
</s>
<s>
Any	O
of	O
the	O
recovery	O
files	O
can	O
be	O
used	O
to	O
rebuild	O
a	O
missing	O
file	O
from	O
an	O
incomplete	O
download	B-Application
.	O
</s>
<s>
Version	O
1	O
became	O
widely	O
used	O
on	O
Usenet	B-Application
,	O
but	O
it	O
did	O
suffer	O
some	O
limitations	O
:	O
</s>
<s>
It	O
was	O
strongly	O
tied	O
to	O
Usenet	B-Application
and	O
it	O
was	O
felt	O
that	O
a	O
more	O
general	O
tool	O
might	O
have	O
a	O
wider	O
audience	O
.	O
</s>
<s>
Version	O
2.0	O
of	O
the	O
Parchive	B-General_Concept
specification	O
was	O
published	O
by	O
Michael	O
Nahas	O
in	O
September	O
2002	O
.	O
</s>
<s>
Peter	O
Clements	O
then	O
went	O
on	O
to	O
write	O
the	O
first	O
two	O
Par2	O
implementations	O
,	O
QuickPar	B-Application
and	O
par2cmdline	O
.	O
</s>
<s>
Yutaka	O
Sawada	O
created	O
MultiPar	B-General_Concept
to	O
supersede	O
QuickPar	B-Application
.	O
</s>
<s>
MultiPar	B-General_Concept
uses	O
par2j.exe	O
(	O
which	O
is	O
partially	O
based	O
on	O
par2cmdline	O
's	O
optimization	O
techniques	O
)	O
to	O
use	O
as	O
MultiPar	B-General_Concept
's	O
backend	O
engine	O
.	O
</s>
<s>
For	O
Par1	O
,	O
the	O
files	O
f1	O
,	O
f2	O
,	O
...	O
,	O
fn	O
,	O
the	O
Parchive	B-General_Concept
consists	O
of	O
an	O
index	O
file	O
(	O
f.par	O
)	O
,	O
which	O
is	O
CRC	O
type	O
file	O
with	O
no	O
recovery	O
blocks	O
,	O
and	O
a	O
number	O
of	O
"	O
parity	B-Error_Name
volumes	O
"	O
(	O
f.p01	O
,	O
f.p02	O
,	O
etc	O
.	O
)	O
.	O
</s>
<s>
Given	O
all	O
of	O
the	O
original	O
files	O
except	O
for	O
one	O
(	O
for	O
example	O
,	O
f2	O
)	O
,	O
it	O
is	O
possible	O
to	O
create	O
the	O
missing	O
f2	O
given	O
all	O
of	O
the	O
other	O
original	O
files	O
and	O
any	O
one	O
of	O
the	O
parity	B-Error_Name
volumes	O
.	O
</s>
<s>
Alternatively	O
,	O
it	O
is	O
possible	O
to	O
recreate	O
two	O
missing	O
files	O
from	O
any	O
two	O
of	O
the	O
parity	B-Error_Name
volumes	O
and	O
so	O
forth	O
.	O
</s>
<s>
If	O
an	O
index	O
file	O
of	O
a	O
download	B-Application
states	O
that	O
4	O
blocks	O
are	O
missing	O
,	O
the	O
easiest	O
way	O
to	O
repair	O
the	O
files	O
would	O
be	O
by	O
downloading	B-Application
filename.vol003	O
+	O
04.PAR2	O
.	O
</s>
<s>
Supports	O
embedding	O
PAR	B-General_Concept
data	O
inside	O
other	O
formats	O
,	O
like	O
ZIP	B-General_Concept
archives	I-General_Concept
or	O
ISO	O
disk	O
images	O
.	O
</s>
<s>
Supports	O
more	O
error	B-Error_Name
correction	I-Error_Name
code	I-Error_Name
algorithms	O
(	O
such	O
as	O
LDPC	B-Error_Name
and	O
sparse	O
random	O
matrix	O
)	O
.	O
</s>
<s>
Replaced	O
the	O
MD5	B-Algorithm
hash	I-Algorithm
function	O
in	O
Par2	O
with	O
BLAKE3	O
.	O
</s>
<s>
(	O
GPLv2	B-License
)	O
—	O
a	O
concurrent	O
(	O
multithreaded	O
)	O
version	O
of	O
par2cmdline	O
0.4	O
using	O
TBB	B-Application
.	O
</s>
<s>
Only	O
compatible	O
with	O
x86	B-Operating_System
based	I-Operating_System
CPUs	O
.	O
</s>
<s>
It	O
is	O
available	O
in	O
the	O
FreeBSD	B-Application
Ports	I-Application
system	O
as	O
.	O
</s>
<s>
Available	O
in	O
the	O
FreeBSD	B-Application
Ports	I-Application
system	O
as	O
.	O
</s>
<s>
is	O
another	O
multithreaded	O
version	O
of	O
par2cmdline	O
using	O
OpenMP	B-Application
,	O
GPLv2	B-License
,	O
or	O
later	O
.	O
</s>
<s>
(	O
CC0	O
)	O
is	O
a	O
high	O
performance	O
,	O
multithreaded	O
PAR2	O
client	O
and	O
Node.js	B-Language
library	O
.	O
</s>
<s>
(	O
LGPL-3.0	B-Application
)	O
—	O
Produce	O
,	O
verify	O
and	O
repair	O
par2	O
files	O
recursively	O
,	O
both	O
on	O
the	O
command	O
line	O
as	O
well	O
as	O
with	O
the	O
aid	O
of	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
.	O
</s>
<s>
It	O
is	O
available	O
in	O
the	O
Python	B-Language
Package	I-Language
Index	I-Language
system	O
as	O
.	O
</s>
<s>
(	O
freeware	O
)	O
—	O
Builds	O
upon	O
QuickPar	B-Application
's	O
features	O
and	O
GUI	B-Application
,	O
and	O
uses	O
Yutaka	O
Sawada	O
's	O
par2j.exe	O
as	O
the	O
PAR2	O
backend	O
.	O
</s>
<s>
MultiPar	B-General_Concept
supports	O
multiple	O
languages	O
by	O
Unicode	O
.	O
</s>
<s>
The	O
name	O
of	O
MultiPar	B-General_Concept
was	O
derived	O
from	O
"	O
multi-lingual	O
PAR	B-General_Concept
client	O
"	O
.	O
</s>
<s>
MultiPar	B-General_Concept
is	O
also	O
verified	O
to	O
work	O
with	O
Wine	B-Application
under	O
TrueOS	B-Application
and	O
Ubuntu	B-Operating_System
,	O
and	O
may	O
work	O
with	O
other	O
operating	O
systems	O
too	O
.	O
</s>
<s>
Although	O
the	O
Par2	O
components	O
are	O
(	O
or	O
will	O
be	O
)	O
open	O
source	O
,	O
the	O
MultiPar	B-General_Concept
GUI	B-Application
on	O
top	O
of	O
them	O
is	O
currently	O
not	O
open	O
source	O
.	O
</s>
<s>
QuickPar	B-Application
(	O
freeware	O
)	O
—	O
unmaintained	O
since	O
2004	O
,	O
superseded	O
by	O
MultiPar	B-General_Concept
.	O
</s>
<s>
—	O
First	O
PAR	B-General_Concept
implementation	O
,	O
unmaintained	O
since	O
2001	O
.	O
</s>
