Keygen
From Wikipedia, the free encyclopedia
A keygen (a portmanteau of "key generator") is a small program that will generate a CD key or serial/registration number for a piece of software or cryptographic algorithm.
Keygens are made available by software cracking groups for free download on various websites dedicated to software piracy.
[edit] How they work
Typically software requests a serial number only during installation. The installation software applies an algebraic expression to the key entered to validate the key. As an example, the algorithm may define that a key entered must contain 5 numbers that have a checksum of 25, and that the key must also contain 3 letters that, when mapped into their numerical equivalents, have a sum of 42.
In order to write a keygen, the author typically uses a disassembler to look at the raw assembly code of the program they are writing the keygen for, checking either the software itself or the installer. Once they have access to the program's code, they can locate the subroutine(s) responsible for verifying that the key entered is valid. Using this knowledge, they can reverse engineer the algorithm used to generate valid keys, which is then incorporated into the keygen.
[edit] Problems with keygens
- See also: Product activation
Aside from ethics and legality, there are two major issues in using keygens: Product activation and online key verification.
Keys generated with a key generator may not work with software that is used online, including downloading software updates. This is because the user must confirm their serial number every time the software connects to the server, and the key may be invalid for various reasons. One reason is that the cracker may have misinterpreted the original algorithm, creating a key that was "good enough" to let the software be installed, but not letting all possible future generated keys be valid. Another reason may be that the software developers only accept keys that they know were distributed with the media during production, or had been issued with an online registration, causing a cryptographically correct key to still be denied. A third reason could be a secondary unpublished algorithm that is used by the vendor, e.g., to extend the previous example, the characters 0, 7, 9, C, and K are never allowed. The software that confirms the key on the user's machine does not know these numbers and characters are not allowed, and will accept the keygen output, but the online confirmation fails. One final reason, used primarily with games with online support, is that the keygen creates a valid key, but the key is already in use by either the person who is using the key legally or someone whose keygen program generated the same key. Another major issue is that keygen software, like any other software obtained from an unverifiable source, can contain viruses or Trojan Horses.
[edit] Origins and cultural impact
Keygens are often "decorated" in a nice way that often includes ASCII or ANSI art images as well as mostly "oldschool" Tracker music.
