Dungeon Master - Clever Floppy Disk Anti-Piracy | MVG

I used to be an Amiga developer back in the 80's and we used a similar method for copy protection. I didn't know it had a name until now :). To understand it, you need to know how the Amiga disk drive controller wrote it's data. The controller couldn't recognize a change in magnetization that occurred too quickly. It used a coding system to prevent too many null bits or too many 1 bits from following each other. So basically if you wanted to write out binary 00001111 , the OS would convert it to something like 001 001 011 011 (this is based on my memory so the actual encoding is probably different). Now with this information, we took control of the hardware directly and bypassed the encoding. We wrote 000000000000 and 111111111111 directly to the disk drive at a certain location. We made sure it would not create an error with the sync marks or track locations, so a copy program would not think anything was wrong. Later, when we read that data the controller would try to make sense out of it and depending on the timing would return a value, which wasn't always the same every time. We would read that location multiple times and look for a change in value. We didn't care what value we got back as long as it was different over multiple reads. If you tried to make a copy of the disk, the copy program would read the value and write it back properly encoded. So when we read the value, it would always come back as the same number. I think later versions of XCopy would perform a deep scan and look for fuzzy bits and write them back to the disk as we did. This is all from my memory, so some details may be a bit "fuzzy" :)

The best thing is that hackers must play the game to detect the next level of protection.

To sum it up: If you bought Dungeon Master you'd play a dungeon crawler. If you pirated it, you'd play a puzzle game instead. :D

When the C64 came out with the 5.25" floppy drive, the DRM that companies would use was so destructive, my father actually started a business repairing the drives that inevitably would fail. What they would do was laser damage a sector or sectors on the master. When the drive read head hit this sector, it would cause the read/write head to "knock" out and back repeatedly, trying to read the sector. After a few seconds, the drive would return an error, one that the software was looking for. You could never physically damage the exact sector that the master had and if I remember correctly, no software copying programs ever defeated it. Only hacking and removing the check itself. In the meantime, this "knocking" of the drive heads would eventually cause the heads to go out of alignment. My father contacted Commodore and eventually convinced them to allow him to be a local repair location for these drives. They sent him the tools and some special disk that when read would allow for manual realignment of the heads. Needless to say, this method wasn't around for too long. Nowadays, it would lead to an almost immediate class action lawsuit. lol

Loved this! Honestly didn't know the specifics of how these copy protection schemes worked so yeah, thanks for enlightening 👍

Me: I couldn't care less about floppy disk DRM Also me: Wow. MVG uploaded a video about floppy disk drm. I've always wondered how that worked

FTL had some of the most clever anti-pirating code. A couple of their other titles: The game SunDog would let you play most of the game, but when you got to the final part a message would appear telling you that you can't see the ending because you are a thief. OIDS was the smartest though. This Choplifter-like game would let you play the game, only the shield recharge would simply not do anything. So you could play the game, and see how cool it was, but it was really, really hard. All of these protections worked in that I eventually did buy all the games. Years later, I worked on a PC game and was in charge of adding anti-pirate code. The code I added was subtle, the jump height was multiplied by 0.95. This made a fairly close jump about 15 minutes or so into the game into an impossible one. Not Spyro by any measure, but still fun to read the boards and see the players discussing that particular jump and asking for advise on how to make it.

Incredible story mate. My love for computers began on my friend's C64 before my parents finally brought me an Amiga 600. It was an incredible time as a kid on those machines. The range of games and going to computer meetups to get copies of games was fun. Piracy was all I knew as a kid who had no money but an obsession for computers and gaming. This video brought back fond memories I'd forgotten. Thx

I remember playing this game, buying it 3 times as I broke one disk, had the disk drive mangle one other copy when the sliding cover spring failed. But I also remember Never buying it again, it was "found out" that you could slow the drive speed down with a small screwdriver to a certain speed, write to a certain set of sectors and that basically duplicated the copy protection. You could tell the "cool hackers" by seeing that their drives had a small hole in the top so that they could adjust the speed without having to open the drive cover.

"Please enter this word: I have no fuc" Some reason i doubt the remainder of that line was not the words the words on page 11 :)

On a CD or DVD pits and lands are NOT directly representing ones and zeros, but the CHANGE from pt to land or land to pit would be a one and NO CHANGE would be teh zero. Just FYI ;)

The Schrödinger's 1/0 bit killed me :D

As my grandfather likes to say, "a locked door only keeps an honest man honest."

11:07 Quantum bit copy protection... dayum! Ahead of their time by 30 years.

One of the better encryption mechanisms I found was on an "F16 Fighter" PC game. The actual executable files were randomised on disk. When loaded into memory & executed. The application pointed to itself as if it were data, Then it decrypted itself using an XOR technique. Then the code executed, then it re-encrypted itself. This meant you could not open the exec with a disassembler to figure out the encryption. As the code on disk was valid but not true. You had to watch it run in memory. Step by step, which took hours, to get to the part of the game in question. To make it worse, a failed check just set a variable. The variable was then checked much later in the game. So you died, millions of instructions later. Making it very hard to find the self-modifying code.

Fuzzybit is a genius anti-piracy solution. Even today it can give you loads of headache.

"I have no fu-" Yeah that is pretty much me when dealing with copy protection.

I used to crack C64 games back in the day. From the classic tape drive buffer protection all the way to copy protection that executed entirely inside the disk drive, cracking was often more fun than the game itself.

1:45 "I have no fuc-" Interesting... I think I can guess how the sentence ended.

This is Doug Bell, the lead developer on Dungeon Master and the mind behind the DM copy protection. Nice video. You got most of it right, except the part about the fuzzy bits. The disk protection was actually more sophisticated than the fuzzy bits used by other games at the time. Instead of one or more “random” bits (bits written with a magnetic signature on the threshold between a 1 and a 0), the bits on the sector were simply smaller than a normal bit. The position of the magnetic signature was moved in a sinusoidal pattern from one side of the track to the other side and back. This meant that the disk controller would start reading 1s (or 0s) and at some point switch to reading the opposite. So instead of random bits, it would read random length sequences of bits. This was important because a fuzzy bit could be created by a standard disk drive by toggling the write head on and off while it was writing. The bits on the Dungeon Master disk can only be written by one particular brand of disk duplicator that cost $40,000 at the time.