Case studies in copy protection (opens in new tab)

look-up-a-word-in-the-manual copy protection.

Working Model, a physics simulator for the 68K Mac, did that. "Enter the last word on page NNN". For one release, the manual got some minor modification just before printing, changing the pagination of the last chapters. If the page number was in the first 3/4 of the book, it worked, but if in the last quarter, it didn't. Paying customers very annoyed.

It's a shame this article doesn't cover the UK. There were two notable copy protection schemes from the early 1980s which relied on a physical device.

One was the colour chart supplied with Jet Set Willy (http://steveremembers.tumblr.com/post/90840692306/the-jet-se...). When the game started it gave you a location on the chart and you had to type in the colour. It was difficult at that time to make colour photocopies.

The second was the Lenslok (https://en.wikipedia.org/wiki/Lenslok http://birdsanctuary.co.uk/lenslok/) which was an absolutely atrocious system - more information in the Wikipedia article.

Maher concludes that this was successful due to 'asymmetry' between the devices that wrote the disk and the ones that read it had different capabilities, but the actual reason is probably due to the creativity and complexity of the scheme. Not only did the game have a section of code that was more or less impossible to duplicate, the instructions to validate the code were hidden in unlikely places, and (perhaps the most important point) the game did not immediately fail if it detected that it had been pirated. Every 'definitely cracked' copy circulated increased the demand for an actual working version of the game.

It's crucial that Dungeon Master was an excellent game[0] because otherwise, players might have simply decided it wasn't worth their time or money.

[0]https://en.wikipedia.org/wiki/Dungeon_Master_%28video_game%2...