Product key
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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.
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[edit] Effectiveness
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 (see Controversy).
[edit] Controversy
Some of the most effective CD key protection is very controversial, due to inconvenience, strict enforcement, harsh penalties and, in some cases, false positives. CD key protection has been likened to Digital Rights Management, in that it uses uncompromising digital procedures to enforce the license agreement.
[edit] Inconvenience
Product keys are considered somewhat inconvenient for all end users. Not only do they need to be entered whenever a program is installed, but the user must also be sure not to lose them. Loss of a product key usually means the software is useless once uninstalled.
Product keys also present new ways for distribution to go wrong. If a product is shipped with missing or invalid keys, then the CD itself is useless. For example, all copies of Splinter Cell: Pandora Tomorrow originally shipped to Australia were shipped without CD keys.[1]
[edit] Strict enforcement and harsh penalties
There are many cases of permanent bans enforced by companies detecting usage violations. It is common for an online system to immediately blacklist a CD key caught running cracks or, in some cases (such as Valve Software's Steam content delivery system), cheats. This results in a permanent ban. Players who wish to continue use of the software must repurchase it. This has inevitably led to criticism over the motivations of enforcing permanent bans.
Particularly controversial is the situation which arises when multiple products' keys are bound together. If products have dependencies on other products (as is the case with expansion packs), it is common for companies to ban all bound products. For example, if a fake CD key is used with an expansion pack, the server may ban legitimate CD keys from the original game. Similarly, with Valve's Steam service, all products the user has purchased are bound into the one account. If this account is banned, every product will be rendered unusable[2].
This "multi-ban" is highly controversial, since it bans users from products which they have legitimately purchased and used.
[edit] False positives
Bans are enforced by servers immediately upon detection of cracks or cheats, usually without human intervention. Sometimes, legitimate users are wrongly deemed in violation of the license, and banned. In large cases of false positives, they are sometimes corrected (as happened in World of Warcraft [3]). However, individual cases may not be given any attention.
A common cause of false positives (as with the World of Warcraft case above) is users of unsupported platforms. For example, users of Linux commonly run Windows applications through compatibility layers such as Wine and Cedega. These unexpected environments sometimes appear to the server as cracks, resulting in a ban.
[edit] Recovering product keys
One of the most common problems with companies using the product key method, is that many can either be misplaced or lost by the user. Users that wish to recover a product key may be able to do so by contacting the respective company that owns the piece of software[citation needed], or either by recovering the key via a third party software application.
