<s>
In	O
cryptography	O
,	O
MultiSwap	B-Algorithm
is	O
a	O
block	O
cipher/MAC	O
created	O
by	O
Microsoft	O
in	O
1999	O
as	O
part	O
of	O
its	O
Windows	O
Media	O
DRM	O
service	O
(	O
WMDRM	O
)	O
.	O
</s>
<s>
Microsoft	O
's	O
internal	O
name	O
for	O
the	O
algorithm	O
is	O
not	O
publicly	O
known	O
;	O
it	O
was	O
dubbed	O
MultiSwap	B-Algorithm
in	O
a	O
2001	O
report	O
on	O
WMDRM	O
under	O
the	O
pseudonym	O
"	O
Beale	O
Screamer	O
"	O
.	O
</s>
<s>
The	O
name	O
MultiSwap	B-Algorithm
comes	O
from	O
the	O
cipher	O
's	O
multiplications	O
and	O
swaps	O
.	O
</s>
<s>
WMDRM	O
uses	O
this	O
algorithm	O
only	O
as	O
a	O
MAC	B-Algorithm
,	O
never	O
for	O
encryption	O
.	O
</s>
<s>
applied	O
a	O
multiplicative	O
form	O
of	O
differential	O
cryptanalysis	O
to	O
break	O
MultiSwap	B-Algorithm
.	O
</s>
