<s>
In	O
cryptography	O
,	O
rotational	B-General_Concept
cryptanalysis	I-General_Concept
is	O
a	O
generic	O
cryptanalytic	O
attack	O
against	O
algorithms	O
that	O
rely	O
on	O
three	O
operations	O
:	O
modular	O
addition	O
,	O
rotation	B-Algorithm
and	O
XOR	O
ARX	O
for	O
short	O
.	O
</s>
<s>
The	O
basic	O
idea	O
of	O
rotational	B-General_Concept
cryptanalysis	I-General_Concept
is	O
that	O
both	O
the	O
bit	O
rotation	B-Algorithm
and	O
XOR	O
operations	O
preserve	O
correlations	O
between	O
bit-rotated	O
pairs	O
of	O
inputs	O
,	O
and	O
that	O
addition	O
of	O
bit-rotated	O
inputs	O
also	O
partially	O
preserves	O
bit	O
rotation	B-Algorithm
correlations	O
.	O
</s>
<s>
in	O
2010	O
paper	O
"	O
Rotational	B-General_Concept
Cryptanalysis	I-General_Concept
of	O
ARX	O
"	O
,	O
which	O
presented	O
the	O
best	O
cryptanalytic	O
attacks	O
at	O
that	O
time	O
against	O
a	O
reduced-round	O
Threefish	B-Algorithm
cipher	O
part	O
of	O
the	O
Skein	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
,	O
a	O
SHA-3	B-Algorithm
competition	I-Algorithm
candidate	O
.	O
</s>
<s>
A	O
follow-up	O
attack	O
from	O
the	O
same	O
authors	O
and	O
Christian	O
Rechberger	O
breaks	O
collision	O
resistance	O
of	O
up	O
to	O
53	O
of	O
72	O
rounds	O
in	O
Skein-256	O
,	O
and	O
57	O
of	O
72	O
rounds	O
in	O
Skein-512	O
.	O
</s>
<s>
It	O
also	O
affects	O
the	O
Threefish	B-Algorithm
cipher	O
.	O
</s>
