Clean room design
Clean room design (also known as the Chinese wall technique) is the method of copying a design by reverse engineering and then recreating it without infringing any of the copyrights and trade secrets associated with the original design. Clean room design is useful as a defense against copyright and trade secret infringement because it relies on independent invention. However, because independent invention is not a defense against patents, clean room designs typically cannot be used to circumvent patent restrictions.
The term implies that the design team works in an environment that is "clean" or demonstrably uncontaminated by any knowledge of the proprietary techniques used by the competitor.
Typically, a clean room design is done by having someone examine the system to be reimplemented and having this person write a specification. This specification is then reviewed by a lawyer to ensure that no copyrighted material is included. The specification is then implemented by a team with no connection to the original examiners.
A famous example is that of Columbia Data Products who built the first clone of an IBM computer through a clean room implementation of its BIOS. Another is VTech's successful clones of the Apple II ROMs for the Laser 128, the only computer model, among dozens of Apple II compatibles, which survived litigation brought by Apple Computer. ReactOS is an open source operating system made from clean room reverse engineered components of Windows.
Case law 
Sony Computer Entertainment, Inc. v. Connectix Corporation was a 1999 lawsuit which established an important precedent in regard to reverse engineering. Sony sought damages for copyright infringement over Connectix's Virtual Game Station emulator, alleging that its proprietary BIOS code had been copied into Connectix's product without permission. Sony won the initial judgment, but the ruling was overturned on appeal. Sony eventually purchased the rights to Virtual Game Station to prevent its further sale and development. This established a precedent addressing the legal implications of commercial reverse engineering efforts.
During production, Connectix unsuccessfully attempted a Chinese wall approach to reverse engineer the BIOS, so its engineers disassembled the object code directly. Connectix's successful appeal maintained that the direct disassembly and observation of proprietary code was necessary because there was no other way to determine its behavior. From the ruling:
Some works are closer to the core of intended copyright protection than others. Sony's BIOS lay at a distance from the core because it contains unprotected aspects that cannot be examined without copying. The court of appeal therefore accorded it a lower degree of protection than more traditional literary works.
See also 
- Sony Computer Entertainment, Inc. v. Connectix Corporation, 203 F.3d 596 (9th Cir. 2000).
- Sony Computer Entertainment, Inc. v. Connectix Corporation, 203 F.3d 596 (9th Cir. 2000). Web Archive.org copy, Feb 28, 2007.
- Computerworld article on clean room design