Reverse engineering

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Reverse engineering (RE) is the process of taking something (a device, an electrical component, a software program, etc.) apart and analyzing its workings in detail, usually with the intention to construct a new device or program that does the same thing without actually copying anything from the original. The verb form is to reverse-engineer, spelled with a hyphen.

Reverse engineering is often used by military in order to copy other nations' technology, parts of which have been obtained by intelligence operations. It was often used during the Second World War and the Cold War.

Reverse engineering software or hardware systems which is done for the purposes of interoperability (for example, to support undocumented file formats or undocumented hardware peripherals), is mostly believed to be legal, though patent owners often contest this and attempt to stifle any reverse engineering of their products for any reason.

Other purposes of reverse engineering include security auditing, removal of copy protection ("cracking"), circumvention of access restrictions often present in consumer electronics, and pure curiosity and customization of embedded systems (such as engine management systems).

Reverse engineering of mechanical components

Mechanical components of mechanical systems, such as motors, or electrical systems, such as plugs, sockets, and edge card connectors can be reproduced by measuring their mechanical characteristics. In the reverse engineering of mechanical components, the shape of the component under scrutiny must be completely and accurately measured. The forces acting upon it must also be analysed in order to ensure that the new component can withstand the forces that the original withstood.

Coordinate-measuring machines (CMM) can be used to create a 3D model of the original component, which can then be used in computer-aided modeling. New and improved techniques in reverse engineering include laser scanning which uses laser beams to scan across the surface of components of any shape and create a very precise image of the component surface. This scanning creates a series of slices that, when combined, can represent the surface of the object in a computer simulation.

Reverse engineering of software

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The term "reverse engineering" as applied to software means different things to different people, prompting Chikofsky and Cross Template:Fn to write a paper researching the various uses and defining a taxonomy. From their paper: "Reverse engineering is the process of analyzing a subject system to create representations of the system at a higher level of abstraction."

It can also be seen as "going backwards through the development cycle" Template:Fn. In this model, the output of the implementation phase (in source code form) is reverse engineered back to the analysis phase, in an inversion of the traditional waterfall model.

Reverse engineering is a process of examination only: the software system under consideration is not modified (which would make it reengineering).

In practice, two main types of reverse engineering emerge. In the first case, source code is already available for the software, but higher level aspects of the program, perhaps poorly documented or documented but no longer valid, are discovered. In the second case, there is no source code available for the software, and any efforts towards discovering one possible source code for the software are regarded as reverse engineering. This second usage of the term is the one most people are familiar with.

Reverse engineering of binary software

This process is sometimes termed Reverse Code Engineering or RCE Template:Fn. As an example, decompilation of binaries for the Java platform can be accomplished using ARGOuml.org. One famous case of reverse engineering was the first non-IBM implementation of BIOS which launched the historic PC clone industry.

In the United States, the Digital Millennium Copyright Act exempts from the circumvention ban some acts of reverse engineering aimed at interoperability of file formats and protocols (17 USC 1201(f)), but judges in key cases have ignored this law, since it is acceptable to circumvent restrictions for use, but not for access.

The Samba software, which allows systems that are not running Microsoft Windows systems to share files with systems that are, is a classic example of software reverse engineering, since the Samba project had to reverse-engineer unpublished information about how Windows file sharing worked, so that non-Windows computers could emulate it. The WINE project does the same thing for the Windows API, and OpenOffice.org is one party doing this for the Microsoft Office file formats.

Techniques

Reverse engineering of software can be accomplished by various methods. The three main groups of software reverse engineering are:

  1. Analysis through observation of information exchange, most prevalent in protocol reverse engineering, which involve using bus analyzers and packet sniffers for example for listening into a computer bus or computer network connection, revealing the traffic data underneath. Behaviour on the bus or network can then be analyzed for producing a stand-alone implementation that mimics the same behaviour. This is especially good for reverse engineering of device drivers.
  2. Disassembly using a disassembler, meaning the raw machine language of the program is read and understood in its own terms, only with the aid of machine language mnemonics. This works on any computer program but can take quite some time, especially for someone not used to machine code.
  3. Decompilation using a decompiler, a process that tries, with varying result, to recreate the source code in some high level language for a program only available in machine code.

Reverse engineering as business research

Reverse engineering is also used by businesses to assess competitors' products. It is used to analyze, for instance, how a competitor's product works, what it does, who manufactures it, what components it consists of, estimate costs, identify potential patent infringement, etc.

Value engineering is a related activity also used by business. It involves deconstructing and analysing products, but the objective is to find opportunities for cost cutting.

Similar tasks

  • Research of physical laws is reverse-engineering the world.
  • Black box testing in software engineering has a lot in common with reverse-engineering, the tester usually has the API, but his goals are to find bugs and undocumented features by bashing the product from outside.

Examples

  • Jerry can. During World War II, British and American forces noticed that the Germans had gasoline cans with an excellent design. They reverse engineered copies of those cans. The cans were popularly known as Jerry cans.
  • The Tupolev Tu-4. During World War II, a number of American B-29 bombers on missions over Japan were forced to land in the USSR. The Soviets, who did not have a similar strategic bomber, decided to copy the B-29. Within a few years they had developed the Tu-4, a near perfect copy.

See also

References

External links

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