A CD key, or product key is a specific software-based key for a certain computer program and is used to identify that the copy of the program is original. For official products the key might be used offline, at other times with software like Windows, it is registered online to prevent multiple people using the same key.

The term CD key likely comes from the fact that the key is usually on the case or the CD. Computer games and Window Install discs come with CD keys to verify that the disc has been not been illegally copied. The key itself consist of a series of numbers and/or letters. This sequence is then passed to a verification function in the program. This function manipulates the key sequence according to a mathematical algorithm and attempts to match the results to a set of valid solutions.

CD Key: Effectiveness

Most CD keys are not effective in stopping software piracy due to the rise of the Internet, as CD keys can be distributed quickly via CD key generators. As a result, software publishers are increasingly turning to new methods of authenticating software, such as via internet authenticating systems.

This article is adapted from: wikiPedia.com.