20 years ago, I added a simple licensing feature to our business software - a readable XML with all the license features and timeframes for them and a signature

20 years ago, I added a simple licensing feature to our business software - a readable XML with all the license features and timeframes for them and a signature. The license was pretty cool as it allowed us to do timed feature sets. Of course, our public key was obfuscated in the code, but it wasn't too hard to replace it. The reason was to keep the honest customers from easy abuse. The readability of the license key was a great plus. This worked very well for us, and we've managed to score some huge customers.