<s>
In	O
cryptography	O
,	O
REDOC	B-Algorithm
II	I-Algorithm
and	O
REDOC	B-Algorithm
III	I-Algorithm
are	O
block	O
ciphers	O
designed	O
by	O
Michael	O
Wood	O
(	O
cryptographer	O
)	O
for	O
Cryptech	O
Inc	O
and	O
are	O
optimised	O
for	O
use	O
in	O
software	O
.	O
</s>
<s>
Both	O
REDOC	B-Algorithm
ciphers	O
are	O
patented	O
.	O
</s>
<s>
REDOC	B-Algorithm
II	I-Algorithm
(	O
Cusick	O
and	O
Wood	O
,	O
1990	O
)	O
operates	O
on	O
80-bit	O
blocks	O
with	O
a	O
160-bit	O
key	O
.	O
</s>
<s>
The	O
cipher	O
has	O
10	O
rounds	O
,	O
and	O
uses	O
key-dependent	O
S-boxes	B-Algorithm
and	O
masks	O
used	O
to	O
select	O
the	O
tables	O
for	O
use	O
in	O
different	O
rounds	O
of	O
the	O
cipher	O
.	O
</s>
<s>
A	O
prize	O
of	O
US$	O
5,000	O
was	O
offered	O
for	O
the	O
best	O
attack	O
on	O
one	O
round	O
of	O
REDOC-II	B-Algorithm
,	O
and	O
$	O
20,000	O
for	O
the	O
best	O
practical	O
known-plaintext	O
attack	O
.	O
</s>
<s>
REDOC	B-Algorithm
III	I-Algorithm
is	O
a	O
more	O
efficient	O
cipher	O
.	O
</s>
<s>
Ken	O
Shirriff	O
describes	O
a	O
differential	O
attack	O
on	O
REDOC-III	B-Algorithm
requiring	O
220	O
chosen	O
plaintexts	O
and	O
230	O
memory	O
.	O
</s>
