An encrypted function is an attempt to provide
mobile code privacy without providing any
tamper-resistant
Tamperproofing, conceptually, is a methodology used to hinder, deter or detect unauthorised access to a device or circumvention of a security system. Since any device or system can be foiled by a person with sufficient knowledge, equipment, and ti ...
hardware. It is a method where in mobile code can carry out
cryptographic primitives even though the code
*is executed in untrusted environments.
*should run autonomously.
Polynomial
In mathematics, a polynomial is an expression consisting of indeterminates (also called variables) and coefficients, that involves only the operations of addition, subtraction, multiplication, and positive-integer powers of variables. An example ...
and
rational functions are
encrypted
In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can deci ...
such that their transformation can again be implemented as programs consisting of
cleartext
In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted.
Overview
With the advent of comp ...
instructions that a
processor
Processor may refer to:
Computing Hardware
* Processor (computing)
**Central processing unit (CPU), the hardware within a computer that executes a program
*** Microprocessor, a central processing unit contained on a single integrated circuit (I ...
or
interpreter understands. The processor would not understand the program's function. This field of study is gaining popularity as ''mobile cryptography''.
Example
Scenario:
Host ''A'', has an
algorithm
In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific problems or to perform a computation. Algorithms are used as specifications for performing ...
which computes function ''f''. ''A'' wants to send its
mobile agent In computer science, a mobile agent is a composition of computer software and data that is able to migrate (move) from one computer to another autonomously and continue its execution on the destination computer. In reality, the mobile agent is the c ...
to ''B'' which holds input ''x'', to compute ''f''(''x''). But ''A'' doesn't want ''B'' to learn anything about ''f''.
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'').
Drawbacks:
Finding appropriate encryption schemes that can transform arbitrary functions is a challenge. The scheme doesn't prevent
denial of service
In computing, a denial-of-service attack (DoS attack) is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connec ...
, replay,
experimental extraction and others.
See also
Homomorphic encryption
Homomorphic encryption is a form of encryption that permits users to perform computations on its encrypted data without first decrypting it. These resulting computations are left in an encrypted form which, when decrypted, result in an identical ...
References
* Thomas Sander and Christian F. Tschudin. ''Protecting Mobile Agents Against Malicious Hosts.'' 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
Cryptography
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