You are running a small software business that sells digital downloads - apps, plugins, or even templates. When the buyer completes the purchase, you need to provide them with a license key that they can use to activate and validate the software. Here’s how you can implement such a licensing system in your software: Generate a public and private key pair using the RSA algorithm. Sign a message with the private key. The message contains the buyer’s email address and the software SKU. The signed message is the license key that is sent back to the buyer’s email address. When the buyer activates the software, the license key is verified using the public key. The Advantages The advantage here is that the public key can be included in the software’s source code, there’s no need to use a database, and the buyer can verify the license key offline without the need to connect to your server. Let’s now go through the implementation steps in detail. 1. Generate Public and Private K