<s>
The	O
Chaocipher	B-Algorithm
is	O
a	O
cipher	B-Application
method	O
invented	O
by	O
John	O
Francis	O
Byrne	O
in	O
1918	O
and	O
described	O
in	O
his	O
1953	O
autobiographical	O
Silent	O
Years	O
.	O
</s>
<s>
He	O
believed	O
Chaocipher	B-Algorithm
was	O
simple	O
,	O
yet	O
unbreakable	O
.	O
</s>
<s>
For	O
90	O
years	O
,	O
the	O
Chaocipher	B-Algorithm
algorithm	O
was	O
a	O
closely	O
guarded	O
secret	O
known	O
only	O
to	O
a	O
handful	O
of	O
persons	O
.	O
</s>
<s>
In	O
May	O
2010	O
Byrne	O
's	O
daughter-in-law	O
,	O
Patricia	O
Byrne	O
,	O
donated	O
all	O
Chaocipher-related	O
papers	O
and	O
artifacts	O
to	O
the	O
National	O
Cryptologic	O
Museum	O
in	O
Ft	O
.	O
Meade	O
,	O
Maryland	O
,	O
USA	O
.	O
</s>
<s>
This	O
led	O
to	O
the	O
disclosure	O
of	O
the	O
Chaocipher	B-Algorithm
algorithm	O
.	O
</s>
<s>
In	O
Byrne	O
's	O
embodiment	O
of	O
Chaocipher	B-Algorithm
,	O
the	O
system	O
consists	O
of	O
two	O
disks	O
,	O
referred	O
to	O
as	O
the	O
left	O
and	O
right	O
disks	O
,	O
each	O
having	O
26	O
equal-sized	O
removable	O
tabs	O
around	O
its	O
periphery	O
.	O
</s>
<s>
In	O
its	O
classic	O
form	O
,	O
the	O
Chaocipher	B-Algorithm
system	O
consists	O
of	O
two	O
alphabets	O
,	O
with	O
the	O
right-side	O
alphabet	O
used	O
for	O
locating	O
the	O
plaintext	O
letter	O
,	O
while	O
the	O
other	O
(	O
"	O
left	O
"	O
)	O
alphabet	O
is	O
used	O
for	O
reading	O
the	O
corresponding	O
ciphertext	O
letter	O
.	O
</s>
<s>
A	O
detailed	O
description	O
of	O
the	O
Chaocipher	B-Algorithm
algorithm	O
is	O
available	O
as	O
well	O
as	O
discussions	O
of	O
the	O
deciphered	O
plaintexts	O
and	O
the	O
solution	O
to	O
Byrne	O
's	O
challenge	O
.	O
</s>
<s>
Read	O
the	O
corresponding	O
ciphertext	O
letter	O
at	O
the	O
zenith	O
position	O
on	O
the	O
cipher	B-Application
(	O
left	O
)	O
disk	O
.	O
</s>
<s>
Note	O
how	O
the	O
left	O
(	O
cipher	B-Application
)	O
disk	O
rotates	O
respectively	O
in	O
the	O
opposite	O
direction	O
.	O
</s>
<s>
The	O
letter	O
in	O
the	O
zenith	O
position	O
on	O
the	O
cipher	B-Application
(	O
left	O
)	O
disk	O
is	O
our	O
ciphertext	O
letter	O
(	O
i.e.	O
,	O
'	O
C	O
 '	O
)	O
.	O
</s>
<s>
See	O
the	O
next	O
section	O
for	O
instructions	O
on	O
performing	O
Chaocipher	B-Algorithm
's	O
unique	O
permuting	O
of	O
the	O
two	O
disks	O
in	O
preparation	O
for	O
enciphering	O
the	O
next	O
plaintext	O
letter	O
.	O
</s>
<s>
Deciphering	O
a	O
Chaocipher-encrypted	O
message	O
is	O
identical	O
to	O
the	O
steps	O
used	O
for	O
enci­phering	O
.	O
</s>
<s>
The	O
sole	O
difference	O
is	O
that	O
the	O
decipherer	O
locates	O
the	O
known	O
ciphertext	O
letter	O
in	O
the	O
left	O
(	O
cipher	B-Application
)	O
disk	O
,	O
reading	O
off	O
the	O
plaintext	O
letter	O
from	O
the	O
right	O
(	O
plain	O
)	O
disk	O
.	O
</s>
<s>
Although	O
John	O
F	O
.	O
Byrne	O
presented	O
Chaocipher	B-Algorithm
challenge	O
messages	O
in	O
his	O
autobiographical	O
"	O
Silent	O
Years	O
"	O
,	O
he	O
never	O
described	O
how	O
the	O
system	O
worked	O
.	O
</s>
<s>
Until	O
2010	O
at	O
least	O
three	O
people	O
knew	O
how	O
it	O
worked	O
:	O
Byrne	O
's	O
son	O
John	O
,	O
and	O
two	O
of	O
the	O
editors	O
of	O
Cryptologia	O
to	O
whom	O
John	O
confided	O
the	O
underlying	O
method	O
in	O
1990	O
(	O
i.e.	O
,	O
Lou	O
Kruh	O
and	O
Cipher	B-Application
Deavours	O
)	O
.	O
</s>
<s>
In	O
August	O
2009	O
,	O
Moshe	O
Rubin	O
located	O
Byrne	O
's	O
daughter-in-law	O
Patricia	O
Byrne	O
(	O
nee	O
Neway	O
)	O
who	O
,	O
in	O
May	O
2010	O
,	O
donated	O
her	O
father-in-law	O
'	O
s	O
Chaocipher	B-Algorithm
artifacts	O
and	O
papers	O
to	O
the	O
National	O
Cryptologic	O
Museum	O
.	O
</s>
