<s>
In	O
cryptography	O
,	O
RC2	B-Algorithm
(	O
also	O
known	O
as	O
ARC2	O
)	O
is	O
a	O
symmetric-key	B-Algorithm
block	O
cipher	B-Application
designed	O
by	O
Ron	O
Rivest	O
in	O
1987	O
.	O
</s>
<s>
"	O
RC	O
"	O
stands	O
for	O
"	O
Ron	O
's	O
Code	O
"	O
or	O
"	O
Rivest	O
Cipher	B-Application
"	O
;	O
other	O
ciphers	B-Application
designed	O
by	O
Rivest	O
include	O
RC4	B-Algorithm
,	O
RC5	B-Algorithm
,	O
and	O
RC6	B-Algorithm
.	O
</s>
<s>
The	O
development	O
of	O
RC2	B-Algorithm
was	O
sponsored	O
by	O
Lotus	O
,	O
who	O
were	O
seeking	O
a	O
custom	O
cipher	B-Application
that	O
,	O
after	O
evaluation	O
by	O
the	O
NSA	O
,	O
could	O
be	O
exported	O
as	O
part	O
of	O
their	O
Lotus	B-Operating_System
Notes	I-Operating_System
software	O
.	O
</s>
<s>
After	O
further	O
negotiations	O
,	O
the	O
cipher	B-Application
was	O
approved	O
for	O
export	O
in	O
1989	O
.	O
</s>
<s>
Along	O
with	O
RC4	B-Algorithm
,	O
RC2	B-Algorithm
with	O
a	O
40-bit	O
key	O
size	O
was	O
treated	O
favourably	O
under	O
US	O
export	O
regulations	O
for	O
cryptography	O
.	O
</s>
<s>
Initially	O
,	O
the	O
details	O
of	O
the	O
algorithm	O
were	O
kept	O
secret	O
proprietary	O
to	O
RSA	O
Security	O
but	O
on	O
29	O
January	O
1996	O
,	O
source	O
code	O
for	O
RC2	B-Algorithm
was	O
anonymously	O
posted	O
to	O
the	O
Internet	O
on	O
the	O
Usenet	B-Application
forum	O
,	O
sci.crypt	B-General_Concept
.	O
</s>
<s>
Mentions	O
of	O
CodeView	B-Application
and	O
SoftICE	B-Application
(	O
popular	O
debuggers	B-Application
)	O
suggest	O
that	O
it	O
had	O
been	O
reverse	O
engineered	O
.	O
</s>
<s>
A	O
similar	O
disclosure	O
had	O
occurred	O
earlier	O
with	O
RC4	B-Algorithm
.	O
</s>
<s>
In	O
March	O
1998	O
Ron	O
Rivest	O
authored	O
an	O
RFC	O
publicly	O
describing	O
RC2	B-Algorithm
himself	O
.	O
</s>
<s>
RC2	B-Algorithm
is	O
a	O
64-bit	O
block	O
cipher	B-Application
with	O
a	O
variable	O
size	O
key	O
.	O
</s>
<s>
Its	O
18	O
rounds	O
are	O
arranged	O
as	O
a	O
source-heavy	O
unbalanced	B-Algorithm
Feistel	I-Algorithm
network	I-Algorithm
,	O
with	O
16	O
rounds	O
of	O
one	O
type	O
(	O
MIXING	O
)	O
punctuated	O
by	O
two	O
rounds	O
of	O
another	O
type	O
(	O
MASHING	O
)	O
.	O
</s>
<s>
RC2	B-Algorithm
is	O
vulnerable	O
to	O
a	O
related-key	O
attack	O
using	O
234	O
chosen	O
plaintexts	O
.	O
</s>
