<s>
In	O
cryptography	O
,	O
MDC-2	B-Algorithm
(	O
Modification	B-Algorithm
Detection	I-Algorithm
Code	I-Algorithm
2	O
,	O
sometimes	O
called	O
Meyer	O
–	O
Schilling	O
,	O
standardized	O
in	O
ISO	O
10118-2	O
)	O
is	O
a	O
cryptographic	B-Algorithm
hash	I-Algorithm
function	I-Algorithm
.	O
</s>
<s>
MDC-2	B-Algorithm
is	O
a	O
hash	B-Algorithm
function	I-Algorithm
based	I-Algorithm
on	I-Algorithm
a	I-Algorithm
block	I-Algorithm
cipher	I-Algorithm
with	O
a	O
proof	O
of	O
security	O
in	O
the	O
ideal-cipher	O
model	O
.	O
</s>
<s>
The	O
length	O
of	O
the	O
output	O
hash	B-Algorithm
depends	O
on	O
the	O
underlying	O
block	O
cipher	O
used	O
.	O
</s>
<s>
For	O
a	O
given	O
message	O
to	O
hash	B-Algorithm
and	O
a	O
given	O
block	O
cipher	O
encryption	O
function	O
,	O
the	O
MDC-2	B-Algorithm
algorithm	O
proceeds	O
as	O
follows	O
.	O
</s>
<s>
If	O
where	O
each	O
has	O
size	O
,	O
then	O
the	O
hash	B-Algorithm
of	O
the	O
message	O
is	O
given	O
by	O
:	O
</s>
<s>
When	O
MDC-2	B-Algorithm
uses	O
the	O
DES	B-Algorithm
block	O
cipher	O
,	O
the	O
128-bit	O
(	O
16-byte	O
)	O
MDC-2	B-Algorithm
hashes	B-Algorithm
are	O
typically	O
represented	O
as	O
32-digit	O
hexadecimal	O
numbers	O
.	O
</s>
<s>
The	O
following	O
demonstrates	O
a	O
43-byte	O
ASCII	B-Protocol
input	O
(	O
which	O
is	O
padded	O
with	O
five	O
zero-bytes	O
so	O
its	O
length	O
is	O
a	O
multiple	O
of	O
the	O
DES	B-Algorithm
block	O
size	O
of	O
8	O
bytes	O
)	O
and	O
the	O
corresponding	O
MDC-2	B-Algorithm
hash	B-Algorithm
:	O
</s>
<s>
Even	O
a	O
small	O
change	O
in	O
the	O
message	O
will	O
(	O
with	O
probability	O
)	O
result	O
in	O
a	O
completely	O
different	O
hash	B-Algorithm
,	O
e.g.	O
</s>
<s>
The	O
hash	B-Algorithm
of	O
the	O
zero-length	O
string	O
is	O
:	O
</s>
<s>
MDC-2	B-Algorithm
was	O
covered	O
by	O
,	O
issued	O
on	O
March	O
13	O
,	O
1990	O
but	O
filed	O
by	O
IBM	O
on	O
August	O
28	O
,	O
1987	O
.	O
</s>
<s>
Because	O
of	O
patent	O
concerns	O
support	O
for	O
MDC-2	B-Algorithm
has	O
been	O
disabled	O
in	O
OpenSSL	B-Language
on	O
most	O
Linux	B-Application
distributions	O
and	O
is	O
not	O
implemented	O
by	O
many	O
other	O
cryptographic	O
libraries	O
.	O
</s>
<s>
It	O
is	O
implemented	O
in	O
GPG	B-Application
's	I-Application
libgcrypt	O
.	O
</s>
<s>
The	O
Canadian	O
patent	O
was	O
not	O
renewed	O
and	O
no	O
European	O
patent	O
was	O
granted	O
so	O
MDC-2	B-Algorithm
can	O
now	O
be	O
freely	O
used	O
.	O
</s>
