<s>
An	O
encrypted	B-General_Concept
function	I-General_Concept
is	O
an	O
attempt	O
to	O
provide	O
mobile	B-Operating_System
code	I-Operating_System
privacy	O
without	O
providing	O
any	O
tamper-resistant	O
hardware	O
.	O
</s>
<s>
Polynomial	O
and	O
rational	O
functions	O
are	O
encrypted	O
such	O
that	O
their	O
transformation	O
can	O
again	O
be	O
implemented	O
as	O
programs	O
consisting	O
of	O
cleartext	O
instructions	O
that	O
a	O
processor	B-General_Concept
or	O
interpreter	B-Application
understands	O
.	O
</s>
<s>
The	O
processor	B-General_Concept
would	O
not	O
understand	O
the	O
program	O
's	O
function	O
.	O
</s>
<s>
This	O
field	O
of	O
study	O
is	O
gaining	O
popularity	O
as	O
mobile	B-General_Concept
cryptography	I-General_Concept
.	O
</s>
<s>
Host	O
A	O
,	O
has	O
an	O
algorithm	O
which	O
computes	O
function	O
f	O
.	O
A	O
wants	O
to	O
send	O
its	O
mobile	B-Operating_System
agent	I-Operating_System
to	O
B	O
which	O
holds	O
input	O
x	O
,	O
to	O
compute	O
f(x )	O
.	O
</s>
