4 ms·

I wrote some copy protection code for a couple of game cartridges (the idea was to prevent people from trivially copying them into RAM). One cart protected its

by kabdib 12y ago

I wrote some copy protection code for a couple of game cartridges (the idea was to prevent people from trivially copying them into RAM). One cart protected itself with checksums, computed over time from interrupt code, that were the key to decrypt a piece of code that did the "am I running from RAM instead of ROM?" check. Took me two weeks to write (I had two weeks of hanging around waiting for play testing to finish). The software pirate who lived in my apartment complex knew I worked at Atari, and we were chatting one day when I mentioned that I'd written that particular cartridge. He lit up. "Yeah, that was a hard one. Took us three days to crack." Copy-protection can be useful, but it's definitely an asymmetric game.

smosher_ 12y ago
> it's definitely an asymmetric game. This. The crackers have to deal with whatever measures were taken by the authors. On the other hand, the authors have to deal with all of the measures available to everyone interested in cracking it.
rando3826 12y ago
I'm sceptical that the person hacking your console lived in the same apartment complex.
- gaius 12y ago
  Games was a much smaller world back then, and pretty much everyone with a 8-bit system had tried their hand at both writing games and hacking other peoples. When you write assembly language yourself, and own a debugger, then everything is "open source".
  - wiz21 12y ago
    Well, not for me :-) I cracked a few games, looked at someone else's code but I can assure you that at the ASM level, it's very hard to understand that phong-shading routine to the point you can actually re-code it yourself... (yes, I've tried :-)) stF
    - kabdib 12y ago
      Depends on the game. Some games had so few comments that they looked pretty much like a disassembly (Pac-Man for the Atari 800 had exactly two comments in it -- one was a copyright statement, the other was "Ha!", on the critical write-to-ROM for its rather pathetic implementation of copy protection).
- kabdib 12y ago
  175 Calvert Drive in Cupertino. Kind of a dump in the early 80s, probably all condos now [checks . . . nope, still there. Yuck]. I think one of us noticed the other carrying some Atari equipment in the parking lot, and we started chatting. Sure, a bit unlikely, but this was Silly Valley. I think the guy worked for Lockheed and cracking software was a hobby. I kind of had this fellow in mind when I wrote the protection code. I figured it wouldn't stand up very long, and in fact, three days was a moral victory as far as I was concerned. I think he had as much fun with the code as I did :-)
  - rando3826 12y ago
    > Silly Valley Fair enough. I suppose that term will stay in my head now.
belorn 12y ago
I am curious, do you feel the time spent on copy protection was worth it given the result?
- kabdib 12y ago
  Oh yes, definitely. 1. The game got great reviews, so quality did not suffer. 2. In the 1980s, distribution of cracked titles was mostly by modem (BBS) or warez disks, and thus a LOT slower than today. Cracks would take weeks or months to get wide distribution. 3. Atari was paying me $30K/year. Let's double that for total employee load. It took me two weeks to write the copy protection, so that's roughly $2500 cost to Atari. 4. I think Atari's profit on carts was about $25. So to break even we had to deter 100 people from pirating the game and just buy it instead. You can wiggle the profit numbers around if you like, but it doesn't change them appreciably -- it's just not that many buyers that we have to swing in order to pay for development. It's impossible to get numbers, but the fact that the game wasn't trivially copyable by the kid down the street (it took an expert cracker 3 days), that cracks were hard to obtain (little inter-pirate communication, bad distribution systems), and that the title sold maybe a million copies makes it almost certain that the protection not only paid for itself, but did so many times over.

by kabdib 12y ago

smosher_ 12y ago

> it's definitely an asymmetric game. This. The crackers have to deal with whatever measures were taken by the authors. On the other hand, the authors have to deal with all of the measures available to everyone interested in cracking it.

rando3826 12y ago

I'm sceptical that the person hacking your console lived in the same apartment complex.

gaius 12y ago
Games was a much smaller world back then, and pretty much everyone with a 8-bit system had tried their hand at both writing games and hacking other peoples. When you write assembly language yourself, and own a debugger, then everything is "open source".
- wiz21 12y ago
  Well, not for me :-) I cracked a few games, looked at someone else's code but I can assure you that at the ASM level, it's very hard to understand that phong-shading routine to the point you can actually re-code it yourself... (yes, I've tried :-)) stF
  - kabdib 12y ago
    Depends on the game. Some games had so few comments that they looked pretty much like a disassembly (Pac-Man for the Atari 800 had exactly two comments in it -- one was a copyright statement, the other was "Ha!", on the critical write-to-ROM for its rather pathetic implementation of copy protection).
kabdib 12y ago
175 Calvert Drive in Cupertino. Kind of a dump in the early 80s, probably all condos now [checks . . . nope, still there. Yuck]. I think one of us noticed the other carrying some Atari equipment in the parking lot, and we started chatting. Sure, a bit unlikely, but this was Silly Valley. I think the guy worked for Lockheed and cracking software was a hobby. I kind of had this fellow in mind when I wrote the protection code. I figured it wouldn't stand up very long, and in fact, three days was a moral victory as far as I was concerned. I think he had as much fun with the code as I did :-)
- rando3826 12y ago
  > Silly Valley Fair enough. I suppose that term will stay in my head now.

belorn 12y ago

I am curious, do you feel the time spent on copy protection was worth it given the result?

kabdib 12y ago
Oh yes, definitely. 1. The game got great reviews, so quality did not suffer. 2. In the 1980s, distribution of cracked titles was mostly by modem (BBS) or warez disks, and thus a LOT slower than today. Cracks would take weeks or months to get wide distribution. 3. Atari was paying me $30K/year. Let's double that for total employee load. It took me two weeks to write the copy protection, so that's roughly $2500 cost to Atari. 4. I think Atari's profit on carts was about $25. So to break even we had to deter 100 people from pirating the game and just buy it instead. You can wiggle the profit numbers around if you like, but it doesn't change them appreciably -- it's just not that many buyers that we have to swing in order to pay for development. It's impossible to get numbers, but the fact that the game wasn't trivially copyable by the kid down the street (it took an expert cracker 3 days), that cracks were hard to obtain (little inter-pirate communication, bad distribution systems), and that the title sold maybe a million copies makes it almost certain that the protection not only paid for itself, but did so many times over.