<s>
Grøstl	B-Algorithm
is	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
submitted	O
to	O
the	O
NIST	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
competition	I-Algorithm
by	O
Praveen	O
Gauravaram	O
,	O
Lars	O
Knudsen	O
,	O
Krystian	O
Matusiewicz	O
,	O
Florian	O
Mendel	O
,	O
Christian	O
Rechberger	O
,	O
Martin	O
Schläffer	O
,	O
and	O
Søren	O
S	O
.	O
Thomsen	O
.	O
</s>
<s>
Grøstl	B-Algorithm
was	O
chosen	O
as	O
one	O
of	O
the	O
five	O
finalists	O
of	O
the	O
competition	O
.	O
</s>
<s>
It	O
uses	O
the	O
same	O
S-box	B-Algorithm
as	O
AES	B-Algorithm
in	O
a	O
custom	O
construction	O
.	O
</s>
<s>
The	O
authors	O
claim	O
speeds	O
of	O
up	O
to	O
21.4	O
cycles	O
per	O
byte	O
on	O
an	O
Intel	B-Device
Core	I-Device
2	I-Device
Duo	I-Device
,	O
and	O
9.6	O
cycles/byte	O
on	O
an	O
Intel	O
i7	O
with	O
AES-NI	O
.	O
</s>
<s>
According	O
to	O
the	O
submission	O
document	O
,	O
the	O
name	O
"	O
Grøstl	B-Algorithm
"	O
is	O
a	O
multilingual	O
play-on-words	O
,	O
referring	O
to	O
an	O
Austrian	O
dish	O
that	O
is	O
very	O
similar	O
to	O
hash	B-Algorithm
(	O
food	O
)	O
.	O
</s>
<s>
Like	O
other	O
hash	B-Algorithm
functions	I-Algorithm
in	O
the	O
MD5/SHA	O
family	O
,	O
Grøstl	B-Algorithm
divides	O
the	O
input	O
into	O
blocks	O
and	O
iteratively	O
computes	O
hi	O
=	O
f( hi−1	O
,	O
mi	O
)	O
.	O
</s>
<s>
However	O
,	O
Grøstl	B-Algorithm
maintains	O
a	O
hash	B-Algorithm
state	O
at	O
least	O
twice	O
the	O
size	O
of	O
the	O
final	O
output	O
(	O
512	O
or	O
1024	O
bits	O
)	O
,	O
which	O
is	O
only	O
truncated	O
at	O
the	O
end	O
of	O
hash	B-Algorithm
computation	O
.	O
</s>
<s>
The	O
permutation	O
functions	O
P	O
and	O
Q	O
are	O
heavily	O
based	O
on	O
the	O
Rijndael	B-Algorithm
(	O
AES	B-Algorithm
)	O
block	O
cipher	O
,	O
but	O
operate	O
on	O
8×8	O
or	O
8×16	O
arrays	O
of	O
bytes	O
,	O
rather	O
than	O
4×4	O
.	O
</s>
<s>
Like	O
AES	B-Algorithm
,	O
each	O
round	O
consists	O
of	O
four	O
operations	O
:	O
</s>
<s>
Unlike	O
Rijndael	B-Algorithm
,	O
all	O
rounds	O
are	O
identical	O
and	O
there	O
is	O
no	O
final	O
AddRoundKey	O
operation	O
.	O
</s>
<s>
Hash	B-Algorithm
values	O
of	O
empty	O
string	O
.	O
</s>
<s>
Even	O
a	O
small	O
change	O
in	O
the	O
message	O
will	O
(	O
with	O
overwhelming	O
probability	O
)	O
result	O
in	O
a	O
mostly	O
different	O
hash	B-Algorithm
,	O
due	O
to	O
the	O
avalanche	O
effect	O
.	O
</s>
