They were not random; they were mathematically generated. Nero AG used an offline validation algorithm. When you entered a key, the software performed a checksum calculation. If the math added up, the software unlocked.
If you find a website offering a "Nero 711 100 serial number top for free," you will likely run into one of three problems: nero 711 100 serial number top
"I told you, it’s not here," the foreman grunted, spitting a wad of tobacco onto the concrete. "That model was discontinued before the Collapse. Most were melted down for scrap." They were not random; they were mathematically generated
Software keys are usually found on the back of the CD sleeve or in your purchase confirmation email. They were not random