Circumvent a license key

A friend developed an application, that was protected by a license key. Since I was curious how he implemented the key-checking and the application overall I decided to hack the app and write a key generator to use the app. The application was written in java, I looked out for a java decompiler and finally used the „java decompiler“ application. As a result I had a lot of java files. The only problem is, that the naming wasn’t useful at all. For example „class a“ doesn’t say anything about the class. So it took me a while to understand the main parts of the code. I used the information that the UI of the application provides for example certain strings to get a clue where the key verification took place. After i found the key verification it was quite easy to write a key generator, since there it was based on simple math.
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