<s>
The	O
VIC	B-Algorithm
cipher	I-Algorithm
was	O
a	O
pencil	O
and	O
paper	O
cipher	B-Application
used	O
by	O
the	O
Soviet	O
spy	O
Reino	O
Häyhänen	O
,	O
codenamed	O
"	O
VICTOR	O
"	O
.	O
</s>
<s>
If	O
the	O
cipher	B-Application
were	O
to	O
be	O
given	O
a	O
modern	O
technical	O
name	O
,	O
it	O
would	O
be	O
known	O
as	O
a	O
"	O
straddling	O
bipartite	O
monoalphabetic	O
substitution	O
superenciphered	O
by	O
modified	O
double	O
transposition.	O
"	O
</s>
<s>
However	O
,	O
by	O
general	O
classification	O
it	O
is	O
part	O
of	O
the	O
Nihilist	B-Algorithm
family	I-Algorithm
of	O
ciphers	B-Application
.	O
</s>
<s>
It	O
was	O
arguably	O
the	O
most	O
complex	O
hand-operated	O
cipher	B-Application
ever	O
seen	O
,	O
when	O
it	O
was	O
first	O
discovered	O
.	O
</s>
<s>
The	O
initial	O
analysis	O
done	O
by	O
the	O
American	O
National	O
Security	O
Agency	O
(	O
NSA	O
)	O
in	O
1953	O
did	O
not	O
absolutely	O
conclude	O
that	O
it	O
was	O
a	O
hand	O
cipher	B-Application
,	O
but	O
its	O
placement	O
in	O
a	O
hollowed	O
out	O
5¢	O
coin	O
(	O
later	O
known	O
as	O
the	O
Hollow	O
Nickel	O
Case	O
)	O
implied	O
it	O
could	O
be	O
decoded	O
using	O
pencil	O
and	O
paper	O
.	O
</s>
<s>
The	O
VIC	B-Algorithm
cipher	I-Algorithm
remained	O
unbroken	O
until	O
more	O
information	O
about	O
its	O
structure	O
was	O
available	O
.	O
</s>
<s>
Although	O
certainly	O
not	O
as	O
complex	O
or	O
secure	O
as	O
modern	O
computer	O
operated	O
stream	B-Algorithm
ciphers	I-Algorithm
or	O
block	O
ciphers	B-Application
,	O
in	O
practice	O
messages	O
protected	O
by	O
it	O
resisted	O
all	O
attempts	O
at	O
cryptanalysis	O
by	O
at	O
least	O
the	O
NSA	O
from	O
its	O
discovery	O
in	O
1953	O
until	O
Häyhänen	O
's	O
defection	O
in	O
1957	O
.	O
</s>
<s>
The	O
VIC	B-Algorithm
cipher	I-Algorithm
can	O
be	O
regarded	O
as	O
the	O
evolutionary	O
pinnacle	O
of	O
the	O
Nihilist	B-Algorithm
cipher	I-Algorithm
family	O
.	O
</s>
<s>
The	O
VIC	B-Algorithm
cipher	I-Algorithm
has	O
several	O
important	O
integrated	O
components	O
,	O
including	O
mod	O
10	O
chain	O
addition	O
,	O
a	O
lagged	B-Algorithm
Fibonacci	I-Algorithm
generator	I-Algorithm
(	O
a	O
recursive	O
formula	O
used	O
to	O
generate	O
a	O
sequence	O
of	O
pseudorandom	B-Error_Name
digits	O
)	O
,	O
a	O
straddling	B-Algorithm
checkerboard	I-Algorithm
,	O
and	O
a	O
disrupted	O
double	B-Algorithm
transposition	I-Algorithm
.	O
</s>
<s>
Until	O
the	O
discovery	O
of	O
VIC	O
,	O
it	O
was	O
generally	O
thought	O
that	O
a	O
double	B-Algorithm
transposition	I-Algorithm
alone	O
was	O
the	O
most	O
complex	O
cipher	B-Application
an	O
agent	O
,	O
as	O
a	O
practical	O
matter	O
,	O
could	O
use	O
as	O
a	O
field	O
cipher	B-Application
.	O
</s>
<s>
During	O
World	O
War	O
II	O
,	O
several	O
Soviet	O
spy	O
rings	O
communicated	O
to	O
Moscow	O
Centre	O
using	O
two	O
ciphers	B-Application
which	O
are	O
essentially	O
evolutionary	O
improvements	O
on	O
the	O
basic	O
Nihilist	B-Algorithm
cipher	I-Algorithm
.	O
</s>
<s>
A	O
very	O
strong	O
version	O
was	O
used	O
by	O
Max	O
Clausen	O
in	O
Richard	O
Sorge	O
's	O
network	O
in	O
Japan	O
,	O
and	O
by	O
Alexander	O
Foote	O
in	O
the	O
Lucy	O
spy	O
ring	O
in	O
Switzerland	B-Protocol
.	O
</s>
<s>
In	O
both	O
versions	O
,	O
the	O
plaintext	O
was	O
first	O
converted	O
to	O
digits	O
by	O
use	O
of	O
a	O
straddling	B-Algorithm
checkerboard	I-Algorithm
rather	O
than	O
a	O
Polybius	O
square	O
.	O
</s>
<s>
Shutting	O
down	O
sooner	O
reduces	O
the	O
risk	O
of	O
the	O
operator	O
being	O
found	O
by	O
enemy	O
radio	B-Device
direction	I-Device
finders	I-Device
.	O
</s>
<s>
The	O
standard	O
English	O
straddling	B-Algorithm
checkerboard	I-Algorithm
has	O
28	O
character	O
slots	O
and	O
in	O
this	O
cipher	B-Application
the	O
extra	O
two	O
became	O
"	O
full	O
stop	O
"	O
and	O
"	O
numbers	O
shift	O
"	O
.	O
</s>
<s>
The	O
weaker	O
version	O
generated	O
the	O
additive	O
from	O
the	O
text	O
of	O
a	O
novel	O
or	O
similar	O
book	O
(	O
at	O
least	O
one	O
Rote	O
Kapelle	O
member	O
actually	O
used	O
The	O
Good	O
Soldier	O
Schweik	O
)	O
,	O
This	O
text	O
was	O
converted	O
to	O
a	O
digital	O
additive	O
using	O
a	O
technique	O
similar	O
to	O
a	O
straddling	B-Algorithm
checkerboard	I-Algorithm
.	O
</s>
<s>
The	O
ultimate	O
development	O
along	O
these	O
lines	O
was	O
the	O
VIC	B-Algorithm
cipher	I-Algorithm
,	O
used	O
in	O
the	O
1950s	O
by	O
Reino	O
Häyhänen	O
.	O
</s>
<s>
By	O
this	O
time	O
,	O
most	O
Soviet	O
agents	O
were	O
instead	O
using	O
one-time	B-Algorithm
pads	I-Algorithm
.	O
</s>
<s>
However	O
,	O
despite	O
the	O
theoretical	O
perfection	O
of	O
the	O
one-time	B-Algorithm
pad	I-Algorithm
,	O
in	O
practice	O
they	O
were	O
broken	O
,	O
while	O
VIC	O
was	O
not	O
.	O
</s>
<s>
The	O
one-time	O
cipher	B-Application
could	O
however	O
only	O
be	O
broken	O
when	O
cipher	B-Application
pages	O
were	O
re-used	O
,	O
due	O
to	O
logistic	O
problems	O
,	O
and	O
therefore	O
was	O
no	O
longer	O
truly	O
one-time	O
.	O
</s>
<s>
The	O
cipher	B-Application
broadly	O
worked	O
as	O
follows	O
:	O
</s>
<s>
The	O
last	O
two	O
non-equal	O
digits	O
are	O
added	O
to	O
the	O
agent	O
's	O
personal	O
number	O
to	O
determine	O
the	O
key	O
length	O
of	O
the	O
2	O
transpositions	B-Algorithm
.	O
</s>
<s>
These	O
are	O
used	O
to	O
key	O
the	O
Columnar	O
Transposition	B-Algorithm
.	O
</s>
<s>
These	O
are	O
used	O
to	O
key	O
the	O
Diagonal	O
Transposition	B-Algorithm
.	O
</s>
<s>
Once	O
the	O
key	O
has	O
been	O
generated	O
,	O
the	O
first	O
stage	O
of	O
actually	O
encrypting	O
the	O
Message	O
is	O
to	O
convert	O
it	O
to	O
a	O
series	O
of	O
digits	O
,	O
this	O
is	O
done	O
via	O
a	O
Straddling	B-Algorithm
checkerboard	I-Algorithm
.	O
</s>
<s>
The	O
message	O
is	O
transposed	O
via	O
standard	O
columnar	O
transposition	B-Algorithm
keyed	O
by	O
 [ Line-Q ] 	O
above	O
.	O
</s>
<s>
The	O
message	O
is	O
then	O
transposed	O
via	O
Diagonal	O
Transposition	B-Algorithm
keyed	O
by	O
 [ Line-R ] 	O
above	O
.	O
</s>
<s>
The	O
meaning	O
of	O
'	O
diagonal	O
 '	O
in	O
this	O
case	O
is	O
that	O
triangular	O
disruption	O
zones	O
were	O
employed	O
to	O
make	O
the	O
transposition	B-Algorithm
irregular	O
.	O
</s>
<s>
Modular	O
addition	O
or	O
subtraction	O
,	O
also	O
known	O
as	O
'	O
false	O
adding/subtraction	O
'	O
,	O
in	O
this	O
context	O
(	O
and	O
many	O
pen	O
and	O
paper	O
ciphers	B-Application
)	O
is	O
digit-by-digit	O
addition	O
and	O
subtraction	O
without	O
'	O
carrying	O
 '	O
or	O
'	O
borrowing	O
 '	O
.	O
</s>
<s>
Chain	O
addition	O
is	O
akin	O
to	O
a	O
linear-feedback	B-Architecture
shift	I-Architecture
register	I-Architecture
,	O
whereby	O
a	O
stream	O
of	O
number	O
is	O
generated	O
as	O
an	O
output	O
(	O
and	O
fed	O
back	O
in	O
as	O
an	O
input	O
)	O
to	O
a	O
seed	O
number	O
.	O
</s>
<s>
Within	O
the	O
VIC	B-Algorithm
Cipher	I-Algorithm
chain	O
addition	O
works	O
by	O
(	O
1	O
)	O
taking	O
the	O
original	O
(	O
seed	O
)	O
number	O
,	O
(	O
2	O
)	O
false-adding	O
the	O
first	O
two	O
digits	O
,	O
(	O
3	O
)	O
putting	O
this	O
new	O
number	O
at	O
the	O
end	O
of	O
the	O
chain	O
.	O
</s>
<s>
 [ Line-G ] 	O
in	O
the	O
cipher	B-Application
)	O
with	O
one	O
from	O
a	O
key	O
sequence	O
(	O
i.e.	O
</s>
<s>
To	O
decrypt	O
the	O
VIC	B-Algorithm
Cipher	I-Algorithm
is	O
as	O
follows	O
:	O
</s>
<s>
The	O
cipher	B-Application
is	O
one	O
of	O
the	O
strongest	O
pen	O
and	O
paper	O
ciphers	B-Application
actually	O
used	O
in	O
the	O
real	O
world	O
,	O
and	O
was	O
not	O
broken	O
(	O
in	O
terms	O
of	O
determining	O
the	O
underlying	O
algorithm	O
)	O
by	O
the	O
NSA	O
at	O
the	O
time	O
.	O
</s>
<s>
However	O
,	O
with	O
the	O
advent	O
of	O
modern	O
computing	O
,	O
and	O
public	O
disclosure	O
of	O
the	O
algorithm	O
this	O
would	O
not	O
be	O
considered	O
a	O
strong	O
cipher	B-Application
.	O
</s>
