4 ms·

I wrote some 6502 protection code for Atari game cartridges. The problem was that a cartridge could be copied (trivially), then loaded into RAM at the same addr

by kabdib 11y ago

I wrote some 6502 protection code for Atari game cartridges. The problem was that a cartridge could be copied (trivially), then loaded into RAM at the same address, then run. There were many disks running around with cracks of cartridges that you could just load and run. The goal of the protection code was to detect whether the code was running in RAM or ROM, usually by hiding writes that would cause crashes or be detected by the game logic. Once I had about two weeks to spare on a protection system; it used a couple levels of decryption and some delaying tactics so that the title would crash minutes after starting. A prolific Atari pirate lived in my apartment complex. After the cartridge shipped, I asked him about it. "Oh, that was a hard one. It took me and my friends three days to crack." Time and numbers are not on the side of DRM. (I'm also unconvinced that Atari lost much money to copying).

ddingus 11y ago
Cart protection on 6502 was tough to hide. I personally never reversed one, but a friend and I did a couple for the 6809. That thing was tough! Lots of options, addressing modes, etc... Took weeks, and it was on cassette. I've often wondered about your last bit there. The way it was in my little home town is a lot of people copied stuff. But, they barely could afford the computers too. Those who did have the bucks bought most of the stuff that ended up copied. You might be right, at least early on. Later in the 80's, disk copying was massive. The C64 scene seemed to have buyers, but nearly everyone was on copied media in the Atari scene. Fewer machines, more copies, and it seemed like easier copies too... Some schemes were bad sector ones, and frankly, one could just count the beeps, open the door, wait for the error and continue. Not everyone checked the nature of the error, it seems.

by kabdib 11y ago

ddingus 11y ago

Cart protection on 6502 was tough to hide. I personally never reversed one, but a friend and I did a couple for the 6809. That thing was tough! Lots of options, addressing modes, etc... Took weeks, and it was on cassette. I've often wondered about your last bit there. The way it was in my little home town is a lot of people copied stuff. But, they barely could afford the computers too. Those who did have the bucks bought most of the stuff that ended up copied. You might be right, at least early on. Later in the 80's, disk copying was massive. The C64 scene seemed to have buyers, but nearly everyone was on copied media in the Atari scene. Fewer machines, more copies, and it seemed like easier copies too... Some schemes were bad sector ones, and frankly, one could just count the beeps, open the door, wait for the error and continue. Not everyone checked the nature of the error, it seems.