<s>
Akelarre	B-Algorithm
is	O
a	O
block	O
cipher	O
proposed	O
in	O
1996	O
,	O
combining	O
the	O
basic	O
design	O
of	O
IDEA	B-Algorithm
with	O
ideas	O
from	O
RC5	B-Algorithm
.	O
</s>
<s>
Akelarre	B-Algorithm
is	O
a	O
128-bit	O
block	O
cipher	O
with	O
a	O
variable	O
key-length	O
which	O
must	O
be	O
some	O
multiple	O
of	O
64	O
bits	O
.	O
</s>
<s>
The	O
round	O
function	O
of	O
Akelarre	B-Algorithm
is	O
similar	O
to	O
IDEA	B-Algorithm
in	O
structure	O
.	O
</s>
<s>
After	O
the	O
successful	O
cryptanalysis	O
of	O
Akelarre	B-Algorithm
,	O
its	O
designers	O
responded	O
with	O
an	O
updated	O
variant	O
called	O
Ake98	B-Algorithm
.	O
</s>
<s>
This	O
cipher	O
differs	O
from	O
the	O
original	O
Akelarre	B-Algorithm
in	O
the	O
new	O
AR-box	O
(	O
addition	O
–	O
rotation	O
box	O
)	O
,	O
the	O
swapping	O
of	O
words	O
at	O
the	O
end	O
of	O
a	O
round	O
,	O
and	O
the	O
addition	O
of	O
subkeys	O
at	O
the	O
beginning	O
of	O
each	O
round	O
.	O
</s>
<s>
In	O
2004	O
,	O
Jorge	O
Nakahara	O
,	O
Jr.	O
and	O
Daniel	O
Santana	O
de	O
Freitas	O
found	O
large	O
classes	O
of	O
weak	O
keys	O
for	O
Ake98	B-Algorithm
.	O
</s>
<s>
These	O
weak	O
keys	O
allow	O
a	O
cryptanalysis	O
faster	O
than	O
exhaustive	O
search	O
using	O
only	O
71	O
known	O
plaintexts	O
,	O
for	O
up	O
to	O
11.5	O
rounds	O
of	O
Ake98	B-Algorithm
.	O
</s>
