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<title>Encrypted function</title>
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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Encrypted function</span></span>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="en" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><p>An <b>encrypted function</b> is an attempt to provide <a href="Mobile_code" class="mw-redirect" title="Mobile code">mobile code</a> privacy without providing any <a href="Tamper-resistance" class="mw-redirect" title="Tamper-resistance">tamper-resistant</a> hardware. It is a method where in mobile code can carry out <a href="Cryptography" title="Cryptography">cryptographic</a> primitives.
</p><p><a href="Polynomial_function" class="mw-redirect" title="Polynomial function">Polynomial</a> and <a href="Rational_function" title="Rational function">rational functions</a> are <a href="Encrypted" class="mw-redirect" title="Encrypted">encrypted</a> such that their transformation can again be implemented, as programs consisting of <a href="Cleartext" class="mw-redirect" title="Cleartext">cleartext</a> instructions that a <a href="Central_processing_unit" title="Central processing unit">processor</a> or <a href="Interpreter_(computing)" title="Interpreter (computing)">interpreter</a> understands. The processor would not understand the program's function. This field of study is gaining popularity as mobile cryptography.
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<div class="mw-heading mw-heading2"><h2 id="Example">Example</h2></div>
<p>Scenario:
Host A, has an <a href="Algorithm" title="Algorithm">algorithm</a> which computes function f. A wants to send its <a href="Mobile_agent" title="Mobile agent">mobile agent</a> to B which holds input x, to compute f(x). But A doesn't want B to learn anything about f.
</p><p>Scheme:
Function f is encrypted in a way that results in E(f). Host A then creates another program P(E(f)), which implements E(f), and sends it to B through its agent. B then runs the agent, which computes P(E(f))(x) and returns the result to A. A then decrypts this to get f(x).
</p><p>Drawbacks:
Finding appropriate encryption schemes that can transform arbitrary functions is a challenge. The scheme doesn't prevent <a href="Denial_of_service" class="mw-redirect" title="Denial of service">denial of service</a>, replay, experimental extraction and others.
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<div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2></div>
<ul><li><a href="Homomorphic_encryption" title="Homomorphic encryption">Homomorphic encryption</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>
<ul><li>Thomas Sander and Christian F. Tschudin. <i>Protecting Mobile Agents Against Malicious Hosts.</i> In G. Vigna, editor, Mobile agents and security, volume 1419 of Lecture Notes in Computer Science, pages 44–60. Springer-Verlag, New York, NY, 1998. <a rel="nofollow" class="external autonumber" href="http://citeseer.ist.psu.edu/cache/papers/cs/16015/http:zSzzSzwww.icsi.berkeley.eduzSz~tschudinzSzpszSzma-security.pdf/sander98protecting.pdf">[1]</a></li></ul>
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