<s>
SHACAL-1	B-Algorithm
(	O
originally	O
simply	O
SHACAL	B-Algorithm
)	O
is	O
a	O
160-bit	O
block	O
cipher	O
based	O
on	O
SHA-1	B-Algorithm
,	O
and	O
supports	O
keys	O
from	O
128-bit	O
to	O
512-bit	O
.	O
</s>
<s>
SHACAL-2	B-Algorithm
is	O
a	O
256-bit	O
block	O
cipher	O
based	O
upon	O
the	O
larger	O
hash	B-Algorithm
function	I-Algorithm
SHA-256	B-Algorithm
.	O
</s>
<s>
Both	O
SHACAL-1	B-Algorithm
and	O
SHACAL-2	B-Algorithm
were	O
selected	O
for	O
the	O
second	O
phase	O
of	O
the	O
NESSIE	O
project	O
.	O
</s>
<s>
However	O
,	O
in	O
2003	O
,	O
SHACAL-1	B-Algorithm
was	O
not	O
recommended	O
for	O
the	O
NESSIE	O
portfolio	O
because	O
of	O
concerns	O
about	O
its	O
key	O
schedule	O
,	O
while	O
SHACAL-2	B-Algorithm
was	O
finally	O
selected	O
as	O
one	O
of	O
the	O
17	O
NESSIE	O
finalists	O
.	O
</s>
<s>
SHACAL-1	B-Algorithm
is	O
based	O
on	O
the	O
following	O
observation	O
of	O
SHA-1	B-Algorithm
:	O
</s>
<s>
The	O
hash	B-Algorithm
function	I-Algorithm
SHA-1	B-Algorithm
is	O
designed	O
around	O
a	O
compression	B-Algorithm
function	I-Algorithm
.	O
</s>
<s>
The	O
hash	B-Algorithm
function	I-Algorithm
works	O
by	O
repeatedly	O
calling	O
this	O
compression	B-Algorithm
function	I-Algorithm
with	O
successive	O
512-bit	O
data	O
blocks	O
and	O
each	O
time	O
updating	O
the	O
state	O
accordingly	O
.	O
</s>
<s>
This	O
compression	B-Algorithm
function	I-Algorithm
is	O
easily	O
invertible	O
if	O
the	O
data	O
block	O
is	O
known	O
,	O
i.e.	O
</s>
<s>
given	O
the	O
data	O
block	O
on	O
which	O
it	O
acted	O
and	O
the	O
output	O
of	O
the	O
compression	B-Algorithm
function	I-Algorithm
,	O
one	O
can	O
compute	O
that	O
state	O
that	O
went	O
in	O
.	O
</s>
<s>
SHACAL-1	B-Algorithm
turns	O
the	O
SHA-1	B-Algorithm
compression	B-Algorithm
function	I-Algorithm
into	O
a	O
block	O
cipher	O
by	O
using	O
the	O
state	O
input	O
as	O
the	O
data	O
block	O
and	O
using	O
the	O
data	O
input	O
as	O
the	O
key	O
input	O
.	O
</s>
<s>
In	O
other	O
words	O
,	O
SHACAL-1	B-Algorithm
views	O
the	O
SHA-1	B-Algorithm
compression	B-Algorithm
function	I-Algorithm
as	O
an	O
80-round	O
,	O
160-bit	O
block	O
cipher	O
with	O
a	O
512-bit	O
key	O
.	O
</s>
<s>
SHACAL-1	B-Algorithm
is	O
not	O
intended	O
to	O
be	O
used	O
with	O
keys	O
shorter	O
than	O
128	O
bits	O
.	O
</s>
<s>
In	O
the	O
paper	O
"	O
Related-key	O
rectangle	O
attack	O
on	O
the	O
full	O
SHACAL-1	B-Algorithm
"	O
,	O
2006	O
,	O
Orr	O
Dunkelman	O
,	O
Nathan	O
Keller	O
and	O
Jongsung	O
Kim	O
presented	O
a	O
related-key	O
rectangle	O
attack	O
on	O
the	O
full	O
80	O
rounds	O
of	O
SHACAL-1	B-Algorithm
.	O
</s>
<s>
In	O
the	O
paper	O
"	O
Differential	O
and	O
Rectangle	O
Attacks	O
on	O
Reduced-Round	O
SHACAL-1	B-Algorithm
"	O
,	O
Jiqiang	O
Lu	O
,	O
Jongsung	O
Kim	O
,	O
Nathan	O
Keller	O
and	O
Orr	O
Dunkelman	O
presented	O
rectangle	O
attacks	O
on	O
the	O
first	O
51	O
rounds	O
and	O
a	O
series	O
of	O
52	O
inner	O
rounds	O
of	O
SHACAL-1	B-Algorithm
and	O
presented	O
differential	O
attacks	O
on	O
the	O
first	O
49	O
rounds	O
and	O
a	O
series	O
of	O
55	O
inner	O
rounds	O
of	O
SHACAL-1	B-Algorithm
.	O
</s>
<s>
These	O
are	O
the	O
best	O
currently	O
known	O
cryptanalytic	O
results	O
on	O
SHACAL-1	B-Algorithm
in	O
a	O
single	O
key	O
attack	O
scenario	O
.	O
</s>
<s>
In	O
the	O
paper	O
"	O
Related-Key	O
Rectangle	O
Attack	O
on	O
42-Round	O
SHACAL-2	B-Algorithm
"	O
,	O
Jiqiang	O
Lu	O
,	O
Jongsung	O
Kim	O
,	O
Nathan	O
Keller	O
,	O
Orr	O
Dunkelman	O
presented	O
a	O
related-key	O
rectangle	O
attack	O
on	O
42-round	O
SHACAL-2	B-Algorithm
.	O
</s>
<s>
In	O
2008	O
Lu	O
and	O
Kim	O
presented	O
a	O
related-key	O
rectangle	O
attack	O
on	O
44-round	O
SHACAL-2	B-Algorithm
.	O
</s>
<s>
This	O
is	O
the	O
best	O
currently	O
known	O
cryptanalytic	O
result	O
on	O
SHACAL-2	B-Algorithm
.	O
</s>
