The Cracks, Patches and Keygens are used in Windows to extend the lifetime of the trial period of a software, patching a software to bypass the license check, and to activate a software with illegally generated keys respectively.
Crack
A crack cracks the code of the software to increase the number of days of its trial period. Let’s say, a program gives you a 15 day trail period. The crack made for that software can extend that 15 day trial period limit into something like 365 days or 3650 days by cracking and altering the software code. A crack is an additional software that you have to run after installing the main software. The crack asks the user to browse for the main software installation folder and the main software file inside that folder located inside the Program Files folder in the C: drive of Windows OS. After accessing that file, it alters the code and extends the trail period of that software.
Cracks are most popular for software that do not connect to the internet often such as media converters.
Patch
A patch is a pre-cracked main file of a software. It comes with the main software in a package. Users are instructed to replace the original software with the patch file of that software. Patches excel where cracks fail. Some software periodically check the software license with their server over the internet. The trouble with cracks is that once you’ve cracked a software with a crack, the next time that software connects to the internet, it will check its code with its server. If the software is illegally activated it’ll notify the user that the software is not licensed, and will provide a certain number of days for the user to register it or buy a genuine license. A patch modifies the code and removes the feature that makes the software check the license over the internet.
Patches are most popular for software that access the internet regularly such as download managers.
Keygen
A keygen is limited in its functionality. It lets you create illegal license keys for the software. Each key generated by the keygen may not work i.e., may not register or activate the software. Users, sometimes, need to generate many keys and try them one by one to get the one that works. In case of a keygen, its developer tries to deduce the algorithm used in the main software to generate keys for that specific software, he then uses the same algorithm in his keygen.
Keygens are made for a wide variety of software.
These three types of tools are the roots of Software Piracy and other multitude of computer security related problems. Try to avoid these tools, and always look for the free alternatives. There are many dangers of using pirated software, you can read about them here: