<s>
The	O
algorithm	O
can	O
work	O
with	O
any	O
block	O
size	O
between	O
8	O
and	O
128	O
bytes	B-Application
,	O
and	O
supports	O
key	O
sizes	O
between	O
5	O
and	O
125	O
bytes	B-Application
.	O
</s>
<s>
The	O
algorithm	O
consists	O
of	O
8	O
rounds	O
and	O
has	O
a	O
very	O
complicated	O
key	B-Algorithm
schedule	I-Algorithm
.	O
</s>
<s>
It	O
was	O
submitted	O
in	O
1998	O
by	O
TecApro	O
,	O
a	O
Costa	O
Rican	O
software	O
company	O
,	O
to	O
the	O
AES	B-Algorithm
competition	O
as	O
a	O
candidate	O
to	O
become	O
the	O
Advanced	B-Algorithm
Encryption	I-Algorithm
Standard	I-Algorithm
.	O
</s>
<s>
(	O
1999	O
)	O
found	O
a	O
number	O
of	O
weak	O
key	O
classes	O
for	O
FROG	B-Algorithm
.	O
</s>
<s>
FROG	B-Algorithm
was	O
not	O
selected	O
as	O
a	O
finalist	O
.	O
</s>
<s>
Normally	O
a	O
block	O
cipher	O
applies	O
a	O
fixed	O
sequence	O
of	O
primitive	O
mathematical	O
or	O
logical	O
operators	O
(	O
such	O
as	O
additions	O
,	O
XORs	B-Application
,	O
etc	O
.	O
)	O
</s>
<s>
FROG	B-Algorithm
's	O
design	O
philosophy	O
is	O
to	O
hide	O
the	O
exact	O
sequence	O
of	O
primitive	O
operations	O
even	O
though	O
the	O
cipher	O
itself	O
is	O
known	O
.	O
</s>
<s>
While	O
other	O
ciphers	O
use	O
the	O
secret	O
key	O
only	O
as	O
data	O
(	O
which	O
are	O
combined	O
with	O
the	O
plain	O
text	O
to	O
produce	O
the	O
cipher	O
text	O
)	O
,	O
FROG	B-Algorithm
uses	O
the	O
key	O
both	O
as	O
data	O
and	O
as	O
instructions	O
on	O
how	O
to	O
combine	O
these	O
data	O
.	O
</s>
<s>
In	O
effect	O
an	O
expanded	O
version	O
of	O
the	O
key	O
is	O
used	O
by	O
FROG	B-Algorithm
as	O
a	O
program	O
.	O
</s>
<s>
FROG	B-Algorithm
itself	O
operates	O
as	O
an	O
interpreter	O
that	O
applies	O
this	O
key-dependent	O
program	O
on	O
the	O
plain	O
text	O
to	O
produce	O
the	O
cipher	O
text	O
.	O
</s>
<s>
The	O
FROG	B-Algorithm
key	B-Algorithm
schedule	I-Algorithm
(	O
or	O
internal	O
key	O
)	O
is	O
2304	O
bytes	B-Application
long	O
.	O
</s>
<s>
It	O
is	O
produced	O
recursively	O
by	O
iteratively	O
applying	O
FROG	B-Algorithm
to	O
an	O
empty	O
plain	O
text	O
.	O
</s>
<s>
FROG	B-Algorithm
has	O
8	O
rounds	O
,	O
the	O
operations	O
of	O
each	O
round	O
codified	O
by	O
one	O
record	O
in	O
the	O
internal	O
key	O
.	O
</s>
<s>
All	O
operations	O
are	O
byte-wide	O
and	O
consist	O
of	O
XORs	B-Application
and	O
substitutions	O
.	O
</s>
<s>
FROG	B-Algorithm
is	O
very	O
easy	O
to	O
implement	O
(	O
the	O
reference	O
C	O
version	O
has	O
only	O
about	O
150	O
lines	O
of	O
code	O
)	O
.	O
</s>
<s>
Much	O
of	O
the	O
code	O
needed	O
to	O
implement	O
FROG	B-Algorithm
is	O
used	O
to	O
generate	O
the	O
secret	O
internal	O
key	O
;	O
the	O
internal	O
cipher	O
itself	O
is	O
a	O
very	O
short	O
piece	O
of	O
code	O
.	O
</s>
<s>
It	O
is	O
possible	O
to	O
write	O
an	O
assembly	O
routine	O
of	O
just	O
22	O
machine	O
instructions	O
that	O
does	O
full	O
FROG	B-Algorithm
encryption	O
and	O
decryption	O
.	O
</s>
<s>
The	O
implementation	O
will	O
run	O
well	O
on	O
8	O
bit	O
processors	O
because	O
it	O
uses	O
only	O
byte-level	O
instructions	O
.	O
</s>
<s>
FROG	B-Algorithm
's	O
design	O
philosophy	O
is	O
meant	O
to	O
defend	O
against	O
unforeseen/unknown	O
types	O
of	O
attacks	O
.	O
</s>
<s>
Another	O
flaw	O
of	O
FROG	B-Algorithm
is	O
that	O
the	O
decryption	O
function	O
has	O
a	O
much	O
slower	O
diffusion	O
than	O
the	O
encryption	O
function	O
.	O
</s>
