<s>
The	O
Hierocrypt	B-Algorithm
ciphers	O
are	O
very	O
similar	O
,	O
differing	O
mainly	O
in	O
block	O
size	O
:	O
64	O
bits	O
for	O
Hierocrypt-L1	B-Algorithm
,	O
128	O
bits	O
for	O
Hierocrypt-3	B-Algorithm
.	O
</s>
<s>
Hierocrypt-L1	B-Algorithm
'	O
s	O
key	O
size	O
is	O
128	O
bits	O
,	O
while	O
Hierocrypt-3	B-Algorithm
can	O
use	O
keys	O
of	O
128	O
,	O
192	O
,	O
or	O
256	O
bits	O
.	O
</s>
<s>
The	O
number	O
of	O
rounds	O
of	O
encryption	O
also	O
varies	O
:	O
Hierocrypt-L1	B-Algorithm
uses	O
6.5	O
rounds	O
,	O
and	O
Hierocrypt-3	B-Algorithm
uses	O
6.5	O
,	O
7.5	O
,	O
or	O
8.5	O
,	O
depending	O
on	O
the	O
key	O
size	O
.	O
</s>
<s>
The	O
Hierocrypt	B-Algorithm
ciphers	O
use	O
a	O
nested	O
substitution	B-Algorithm
–	I-Algorithm
permutation	I-Algorithm
network	I-Algorithm
(	O
SPN	B-Algorithm
)	O
structure	O
.	O
</s>
<s>
post-whitening	B-Algorithm
.	O
</s>
<s>
The	O
XS-box	O
,	O
which	O
is	O
shared	O
by	O
the	O
two	O
algorithms	O
,	O
is	O
itself	O
an	O
SPN	B-Algorithm
,	O
consisting	O
of	O
a	O
subkey	O
XOR	B-Application
,	O
an	O
S-box	B-Algorithm
lookup	O
,	O
a	O
linear	O
diffusion	O
,	O
another	O
subkey	O
XOR	B-Application
,	O
and	O
another	O
S-box	B-Algorithm
lookup	O
.	O
</s>
<s>
The	O
diffusion	O
operations	O
use	O
two	O
MDS	B-General_Concept
matrices	I-General_Concept
,	O
and	O
there	O
is	O
a	O
single	O
8×	O
8-bit	O
S-box	B-Algorithm
.	O
</s>
<s>
The	O
key	B-Algorithm
schedule	I-Algorithm
uses	O
the	O
binary	O
expansions	O
of	O
the	O
square	O
roots	O
of	O
some	O
small	O
integers	O
as	O
a	O
source	O
of	O
"	O
nothing	O
up	O
my	O
sleeve	O
numbers	O
"	O
.	O
</s>
<s>
No	O
analysis	O
of	O
the	O
full	O
ciphers	O
has	O
been	O
announced	O
,	O
but	O
certain	O
weaknesses	O
were	O
discovered	O
in	O
the	O
Hierocrypt	B-Algorithm
key	B-Algorithm
schedule	I-Algorithm
,	O
linear	O
relationships	O
between	O
the	O
master	O
key	O
and	O
some	O
subkeys	O
.	O
</s>
<s>
There	O
has	O
also	O
been	O
some	O
success	O
applying	O
integral	B-General_Concept
cryptanalysis	I-General_Concept
to	O
reduced-round	O
Hierocrypt	B-Algorithm
variants	O
;	O
attacks	O
faster	O
than	O
exhaustive	O
search	O
have	O
been	O
found	O
for	O
3.5	O
rounds	O
of	O
each	O
cipher	O
.	O
</s>
