Cd key

A Product key (also referred to as a CD key) is a specific software-based key for a certain program or a computer game. It is used to identify that the copy of the program/game is original. Activation is sometimes done offline simply by entering the key, or with software like Windows XP online activation is required to prevent multiple people using the same key.

Computer games use product keys to verify that the game has not been illegally copied; for example, one could not play Diablo II or Starcraft online without an original/unique product key. Another example is Battlefield 2 or Battlefield 2142 will not allow you to play online when two identical product keys are online at the same time.

Product keys consist of a series of numbers and/or letters. This sequence is typically entered by the user during the installation of computer software, and 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.

Most keys are not effective in stopping copyright infringement of software as these keys can be easily distributed. In addition with improved communication from the rise of the Internet more sophisticated attacks on Keys such as cracks (removing the need for a key) and CD key generators have become common.

Because of this, software publishers are increasingly turning to active methods of verifying that keys are both valid and uncompromised.

These "active methods" usually involve requiring periodical validation of the CD key with an internet server (for games with an online component, such as Battle.net, this is easily done whenever the user signs in). The validation can then be performed on the server side, preventing cracks tampering with it (as they do on the client side). The server can also keep a blacklist of all CD keys known to be invalid or which have explicitly been banned, and deny them access.