<s>
A	O
book	B-Algorithm
cipher	I-Algorithm
,	O
or	O
Ottendorf	B-Algorithm
cipher	I-Algorithm
,	O
is	O
a	O
cipher	B-Application
in	O
which	O
the	O
key	O
is	O
some	O
aspect	O
of	O
a	O
book	O
or	O
other	O
piece	O
of	O
text	O
.	O
</s>
<s>
Traditionally	O
,	O
book	B-Algorithm
ciphers	I-Algorithm
work	O
by	O
replacing	O
words	O
in	O
the	O
plaintext	O
of	O
a	O
message	O
with	O
the	O
location	O
of	O
words	O
from	O
the	O
book	O
being	O
used	O
.	O
</s>
<s>
In	O
this	O
mode	O
,	O
book	B-Algorithm
ciphers	I-Algorithm
are	O
more	O
properly	O
called	O
codes	O
.	O
</s>
<s>
One	O
such	O
method	O
,	O
used	O
in	O
the	O
second	O
Beale	O
cipher	B-Application
,	O
replaces	O
the	O
first	O
letter	O
of	O
a	O
word	O
in	O
the	O
book	O
with	O
that	O
word	O
's	O
position	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
the	O
book	B-Algorithm
cipher	I-Algorithm
is	O
properly	O
a	O
homophonic	O
substitution	O
cipher	B-Application
.	O
</s>
<s>
The	O
main	O
strength	O
of	O
a	O
book	B-Algorithm
cipher	I-Algorithm
is	O
the	O
key	O
.	O
</s>
<s>
The	O
sender	O
and	O
receiver	O
of	O
encoded	O
messages	O
can	O
agree	O
to	O
use	O
any	O
book	O
or	O
other	O
publication	O
available	O
to	O
both	O
of	O
them	O
as	O
the	O
key	O
to	O
their	O
cipher	B-Application
.	O
</s>
<s>
In	O
the	O
context	O
of	O
espionage	O
,	O
a	O
book	B-Algorithm
cipher	I-Algorithm
has	O
a	O
considerable	O
advantage	O
for	O
a	O
spy	O
in	O
enemy	O
territory	O
.	O
</s>
<s>
A	O
conventional	O
codebook	B-Algorithm
,	O
if	O
discovered	O
by	O
the	O
local	O
authorities	O
,	O
instantly	O
incriminates	O
the	O
holder	O
as	O
a	O
spy	O
and	O
gives	O
the	O
authorities	O
the	O
chance	O
of	O
deciphering	O
the	O
code	O
and	O
sending	O
false	O
messages	O
impersonating	O
the	O
agent	O
.	O
</s>
<s>
The	O
drawback	O
to	O
a	O
book	B-Algorithm
cipher	I-Algorithm
is	O
that	O
both	O
parties	O
have	O
to	O
possess	O
an	O
identical	O
copy	O
of	O
the	O
key	O
.	O
</s>
<s>
Another	O
approach	O
is	O
to	O
use	O
a	O
dictionary	O
as	O
the	O
codebook	B-Algorithm
.	O
</s>
<s>
Essentially	O
,	O
the	O
code	O
version	O
of	O
a	O
"	O
book	B-Algorithm
cipher	I-Algorithm
"	O
is	O
just	O
like	O
any	O
other	O
code	O
,	O
but	O
one	O
in	O
which	O
the	O
trouble	O
of	O
preparing	O
and	O
distributing	O
the	O
codebook	B-Algorithm
has	O
been	O
eliminated	O
by	O
using	O
an	O
existing	O
text	O
.	O
</s>
<s>
However	O
this	O
means	O
,	O
as	O
well	O
as	O
being	O
attacked	O
by	O
all	O
the	O
usual	O
means	O
employed	O
against	O
other	O
codes	O
or	O
ciphers	B-Application
,	O
partial	O
solutions	O
may	O
help	O
the	O
cryptanalyst	O
to	O
guess	O
other	O
codewords	O
,	O
or	O
even	O
to	O
break	O
the	O
code	O
completely	O
by	O
identifying	O
the	O
key	O
text	O
.	O
</s>
<s>
This	O
is	O
,	O
however	O
,	O
not	O
the	O
only	O
way	O
a	O
book	B-Algorithm
cipher	I-Algorithm
may	O
be	O
broken	O
.	O
</s>
<s>
It	O
is	O
still	O
susceptible	O
to	O
other	O
methods	O
of	O
cryptanalysis	O
,	O
and	O
as	O
such	O
is	O
quite	O
easily	O
broken	O
,	O
even	O
without	O
sophisticated	O
means	O
,	O
without	O
the	O
cryptanalyst	O
having	O
any	O
idea	O
to	O
what	O
book	O
the	O
cipher	B-Application
is	O
keyed	O
.	O
</s>
<s>
If	O
used	O
carefully	O
,	O
the	O
cipher	B-Application
version	O
is	O
probably	O
much	O
stronger	O
,	O
because	O
it	O
acts	O
as	O
a	O
homophonic	O
cipher	B-Application
with	O
an	O
extremely	O
large	O
number	O
of	O
equivalents	O
.	O
</s>
<s>
A	O
famous	O
use	O
of	O
a	O
book	B-Algorithm
cipher	I-Algorithm
is	O
in	O
the	O
Beale	O
ciphers	B-Application
,	O
of	O
which	O
Document	O
No	O
.	O
</s>
<s>
In	O
the	O
American	O
Revolution	O
,	O
Benedict	O
Arnold	O
used	O
a	O
book	B-Algorithm
cipher	I-Algorithm
,	O
sometimes	O
known	O
as	O
the	O
Arnold	B-Algorithm
Cipher	I-Algorithm
,	O
which	O
used	O
Sir	O
William	O
Blackstone	O
's	O
Commentaries	O
on	O
the	O
Laws	O
of	O
England	O
as	O
a	O
key	O
text	O
.	O
</s>
<s>
Book	B-Algorithm
ciphers	I-Algorithm
have	O
consistently	O
been	O
used	O
throughout	O
the	O
Cicada	O
3301	O
mystery	O
.	O
</s>
<s>
In	O
Colony	O
,	O
a	O
television	O
series	O
,	O
the	O
resistance	O
movement	O
uses	O
a	O
book	B-Algorithm
cipher	I-Algorithm
to	O
communicate	O
between	O
members	O
of	O
the	O
cells	O
.	O
</s>
<s>
In	O
the	O
novel	O
Monsieur	O
Lecoq	O
,	O
published	O
in	O
1868	O
,	O
Monsieur	O
Lecoq	O
finds	O
that	O
a	O
prisoner	O
is	O
communicating	O
with	O
his	O
confederate	O
using	O
a	O
double	O
book	B-Algorithm
cipher	I-Algorithm
.	O
</s>
<s>
In	O
The	O
Valley	O
of	O
Fear	O
,	O
Sherlock	B-Application
Holmes	I-Application
decrypts	O
a	O
message	O
enciphered	O
with	O
a	O
book	B-Algorithm
cipher	I-Algorithm
by	O
deducing	O
which	O
book	O
had	O
been	O
used	O
as	O
a	O
key	O
text	O
.	O
</s>
<s>
The	O
name	O
of	O
Ken	O
Follett	O
's	O
World	O
War	O
II	O
thriller	O
The	O
Key	O
to	O
Rebecca	O
refers	O
to	O
a	O
German	O
spy	O
in	O
Cairo	B-Language
using	O
Daphne	O
du	O
Maurier	O
's	O
novel	O
Rebecca	O
as	O
the	O
basis	O
of	O
a	O
code	O
.	O
</s>
<s>
Graham	O
Greene	O
's	O
protagonists	O
often	O
use	O
book	B-Algorithm
codes	I-Algorithm
.	O
</s>
<s>
A	O
book	B-Algorithm
cipher	I-Algorithm
plays	O
an	O
important	O
role	O
in	O
the	O
TV	O
version	O
of	O
Sharpe	O
's	O
Sword	O
.	O
</s>
<s>
In	O
the	O
2004	O
film	O
National	O
Treasure	O
,	O
an	O
"	O
Ottendorf	B-Algorithm
cipher	I-Algorithm
"	O
is	O
discovered	O
on	O
the	O
back	O
of	O
the	O
U.S.	O
</s>
<s>
The	O
protagonists	O
of	O
the	O
Matthew	O
Reilly	O
novel	O
The	O
Six	O
Sacred	O
Stones	O
used	O
a	O
book	B-Algorithm
cipher	I-Algorithm
to	O
send	O
confidential	O
messages	O
to	O
each	O
other	O
.	O
</s>
<s>
In	O
Lost	O
:	O
Mystery	O
of	O
the	O
Island	O
,	O
a	O
series	O
of	O
four	O
jigsaw	B-Application
puzzles	I-Application
released	O
in	O
2007	O
,	O
Ottendorf	B-Algorithm
cipher	I-Algorithm
was	O
used	O
on	O
each	O
puzzle	O
's	O
box	O
to	O
hide	O
spoilers	O
and	O
reveal	O
information	O
about	O
the	O
show	O
to	O
the	O
fans	O
.	O
</s>
<s>
"	O
The	O
Fisher	O
King	O
"	O
,	O
a	O
two-part	O
episode	O
of	O
Criminal	B-Application
Minds	I-Application
,	O
features	O
an	O
Ottendorf	B-Algorithm
cipher	I-Algorithm
brought	O
to	O
the	O
Behavioral	O
Analysis	O
Unit	O
by	O
the	O
UNSUB	O
via	O
Agent	O
Hotchner	O
's	O
wife	O
.	O
</s>
<s>
In	O
the	O
episode	O
"	O
The	O
Blind	O
Banker	O
"	O
of	O
the	O
BBC	O
series	O
Sherlock	O
,	O
Sherlock	B-Application
Holmes	I-Application
searches	O
for	O
a	O
book	O
that	O
is	O
the	O
key	O
to	O
a	O
cipher	B-Application
being	O
used	O
by	O
Chinese	O
Tong	O
smugglers	O
to	O
communicate	O
with	O
their	O
agents	O
and	O
with	O
each	O
other	O
through	O
graffiti	O
messages	O
.	O
</s>
<s>
In	O
the	O
film	O
Unknown	O
(	O
2011	O
)	O
,	O
Prof	O
.	O
Bressler	O
's	O
passwords	O
are	O
obscured	O
by	O
an	O
Ottendorf	B-Algorithm
cipher	I-Algorithm
.	O
</s>
<s>
In	O
The	O
Unit	O
episode	O
"	O
Paradise	O
Lost	O
"	O
,	O
Jonas	O
Blane	O
(	O
aka	O
Snake	O
Doctor	O
)	O
uses	O
a	O
book	B-Algorithm
code	I-Algorithm
from	O
the	O
poem	O
Paradise	O
Lost	O
to	O
communicate	O
to	O
his	O
wife	O
,	O
Molly	O
,	O
that	O
he	O
has	O
arrived	O
safely	O
in	O
Panama	O
.	O
</s>
<s>
In	O
"	O
The	O
Good	O
Soldier	O
Švejk	O
"	O
by	O
Jaroslav	O
Hašek	O
,	O
the	O
officers	O
in	O
Švejk	O
's	O
battalion	O
attempt	O
to	O
use	O
a	O
book	B-Algorithm
cipher	I-Algorithm
.	O
</s>
<s>
Their	O
attempts	O
are	O
undone	O
,	O
however	O
,	O
when	O
it	O
is	O
revealed	O
that	O
the	O
novel	O
in	O
question	O
is	O
composed	O
of	O
two	O
volumes	O
,	O
and	O
Švejk	O
has	O
delivered	O
the	O
first	O
volume	O
to	O
the	O
officers	O
,	O
thinking	O
that	O
they	O
intended	O
to	O
read	O
the	O
novel	O
,	O
rather	O
than	O
the	O
second	O
,	O
which	O
is	O
used	O
for	O
the	O
cipher	B-Application
.	O
</s>
<s>
Furthermore	O
,	O
the	O
key	O
to	O
the	O
cipher	B-Application
is	O
identical	O
to	O
an	O
example	O
given	O
in	O
a	O
published	O
military	O
textbook	O
.	O
</s>
<s>
In	O
An	O
Instance	O
of	O
the	O
Fingerpost	O
,	O
a	O
historical	O
mystery	O
by	O
Iain	O
Pears	O
,	O
a	O
book	B-Algorithm
cipher	I-Algorithm
conceals	O
one	O
character	O
's	O
family	O
history	O
and	O
its	O
relationship	O
with	O
the	O
English	O
Civil	O
War	O
.	O
</s>
<s>
In	O
John	O
Le	O
Carre	O
's	O
A	O
Perfect	O
Spy	O
,	O
the	O
protagonist	O
Magnus	O
Pym	O
uses	O
a	O
book	B-Algorithm
cipher	I-Algorithm
based	O
on	O
the	O
German	O
text	O
Simplicissimus	O
.	O
</s>
<s>
In	O
the	O
movie	O
Manhunter	O
,	O
Hannibal	O
Lecter	O
,	O
who	O
is	O
in	O
prison	O
,	O
communicates	O
in	O
a	O
personal	O
ad	O
in	O
a	O
newspaper	O
using	O
a	O
book	B-Algorithm
code	I-Algorithm
the	O
police	O
know	O
is	O
not	O
what	O
he	O
says	O
it	O
is	O
(	O
he	O
mentions	O
verses	O
in	O
the	O
Bible	O
,	O
but	O
some	O
of	O
the	O
chapter	O
numbers	O
are	O
not	O
valid	O
.	O
)	O
</s>
<s>
In	O
The	O
Darwin	O
Code	O
by	O
J	O
D	O
Welch	O
,	O
Jess	O
uses	O
a	O
Shakespearean	O
speech	O
to	O
construct	O
a	O
book	B-Algorithm
cipher	I-Algorithm
to	O
communicate	O
with	O
an	O
enemy	O
who	O
may	O
or	O
may	O
not	O
be	O
an	O
ally	O
.	O
</s>
<s>
In	O
the	O
TV	O
series	O
Deutschland	O
83	O
,	O
protagonist	O
Martin	O
Rauch	O
's	O
East	O
German	O
handlers	O
use	O
a	O
book	B-Algorithm
cipher	I-Algorithm
to	O
communicate	O
with	O
him	O
while	O
he	O
is	O
undercover	O
in	O
West	O
Germany	O
.	O
</s>
<s>
In	O
the	O
Series	O
2	O
finale	O
of	O
the	O
BBC	O
TV	O
show	O
Luther	O
,	O
2	O
brothers	O
use	O
a	O
Book	B-Algorithm
Cipher	I-Algorithm
.	O
</s>
<s>
This	O
leads	O
him	O
to	O
discovering	O
the	O
Book	B-Algorithm
Cipher	I-Algorithm
is	O
using	O
Gideon	O
's	O
Bible	O
.	O
</s>
