<s>
In	O
cryptography	O
,	O
RC6	B-Algorithm
(	O
Rivest	O
cipher	O
6	O
)	O
is	O
a	O
symmetric	B-Algorithm
key	I-Algorithm
block	O
cipher	O
derived	O
from	O
RC5	B-Algorithm
.	O
</s>
<s>
It	O
was	O
designed	O
by	O
Ron	O
Rivest	O
,	O
Matt	O
Robshaw	O
,	O
Ray	O
Sidney	O
,	O
and	O
Yiqun	O
Lisa	O
Yin	O
to	O
meet	O
the	O
requirements	O
of	O
the	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
(	O
AES	B-Algorithm
)	O
competition	O
.	O
</s>
<s>
RC6	B-Algorithm
proper	O
has	O
a	O
block	O
size	O
of	O
128	O
bits	O
and	O
supports	O
key	O
sizes	O
of	O
128	O
,	O
192	O
,	O
and	O
256	O
bits	O
up	O
to	O
2040-bits	O
,	O
but	O
,	O
like	O
RC5	B-Algorithm
,	O
it	O
may	O
be	O
parameterised	O
to	O
support	O
a	O
wide	O
variety	O
of	O
word-lengths	O
,	O
key	O
sizes	O
,	O
and	O
number	O
of	O
rounds	O
.	O
</s>
<s>
RC6	B-Algorithm
is	O
very	O
similar	O
to	O
RC5	B-Algorithm
in	O
structure	O
,	O
using	O
data-dependent	O
rotations	O
,	O
modular	O
addition	O
,	O
and	O
XOR	B-Application
operations	O
;	O
in	O
fact	O
,	O
RC6	B-Algorithm
could	O
be	O
viewed	O
as	O
interweaving	O
two	O
parallel	O
RC5	B-Algorithm
encryption	O
processes	O
,	O
although	O
RC6	B-Algorithm
does	O
use	O
an	O
extra	O
multiplication	O
operation	O
not	O
present	O
in	O
RC5	B-Algorithm
in	O
order	O
to	O
make	O
the	O
rotation	O
dependent	O
on	O
every	O
bit	O
in	O
a	O
word	O
,	O
and	O
not	O
just	O
the	O
least	O
significant	O
few	O
bits	O
.	O
</s>
<s>
Note	O
that	O
the	O
key	O
expansion	O
algorithm	O
is	O
practically	O
identical	O
to	O
that	O
of	O
RC5	B-Algorithm
.	O
</s>
<s>
The	O
only	O
difference	O
is	O
that	O
for	O
RC6	B-Algorithm
,	O
more	O
words	O
are	O
derived	O
from	O
the	O
user-supplied	O
key	O
.	O
</s>
<s>
The	O
accompanying	O
instructions	O
revealed	O
that	O
some	O
of	O
these	O
programs	O
use	O
RC6	B-Algorithm
for	O
confidentiality	O
of	O
network	O
communications	O
.	O
</s>
<s>
As	O
RC6	B-Algorithm
was	O
not	O
selected	O
for	O
the	O
AES	B-Algorithm
,	O
it	O
was	O
not	O
guaranteed	O
that	O
RC6	B-Algorithm
is	O
royalty-free	O
.	O
</s>
<s>
,	O
a	O
web	O
page	O
on	O
the	O
official	O
web	O
site	O
of	O
the	O
designers	O
of	O
RC6	B-Algorithm
,	O
RSA	O
Laboratories	O
,	O
states	O
the	O
following	O
:	O
</s>
<s>
"	O
We	O
emphasize	O
that	O
if	O
RC6	B-Algorithm
is	O
selected	O
for	O
the	O
AES	B-Algorithm
,	O
RSA	O
Security	O
will	O
not	O
require	O
any	O
licensing	O
or	O
royalty	O
payments	O
for	O
products	O
using	O
the	O
algorithm	O
"	O
.	O
</s>
<s>
The	O
emphasis	O
on	O
the	O
word	O
"	O
if	O
"	O
suggests	O
that	O
RSA	O
Security	O
Inc	O
.	O
may	O
have	O
required	O
licensing	O
and	O
royalty	O
payments	O
for	O
any	O
products	O
using	O
the	O
RC6	B-Algorithm
algorithm	O
.	O
</s>
<s>
RC6	B-Algorithm
was	O
a	O
patented	O
encryption	O
algorithm	O
(	O
and	O
)	O
;	O
however	O
,	O
the	O
patents	O
expired	O
between	O
2015	O
and	O
2017	O
.	O
</s>
