20 January 2020, 22:33 | #241 |
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On C64 there was some like this:
Code:
label: jmp label I was so baffled when I saw that, that I couldn't believe it. Like they invested probably a good sum in copy protection and then it can be defeated so easily. |
21 January 2020, 00:34 | #242 |
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On Amiga Dungeon Master used a special "fuzzy bit" which were recorder purposely in an instable state (I can't remember in which way, but was possible only through a special hardware, not a regular drive). Different reads were guaranteed to return at least a different value from others, and the game did a check by reading many times in a single burst during the game: if the read were all the same, then the copy were recognized as illegal.
Tech details here: http://dmweb.free.fr/?q=node/210 |
21 January 2020, 03:57 | #243 |
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Dungeon Master wasn't hard to crack because of the fuzzy bit (those routines are easy to spot because they're accessing the drive in a weird way) but because of all the code checksums protecting the protection routines.
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21 January 2020, 09:12 | #244 |
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True, but also because the checks would result in game glitches, instead of some more evident clues, so it was hard to know if a crack was fully working.
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21 January 2020, 12:56 | #245 | |
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I always wondered about that. I thought, that, if I wold write a protected game, I would also trigger the copy protection such that an important item is missing. Like a key to open the door to the next level or such. This is much harder to spot, than some "If copy protected, reboot" or or other easily recognizable action. On the other hand, this might look like a bug to the (illegal) users and wouldn't this create a negative media, if suddenly a lot of users start to report that the game is not working, while this is only exhibiting that they are using a pirated copy? |
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21 January 2020, 14:24 | #246 | |
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21 January 2020, 14:26 | #247 | |
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Due to the nature of the game, you couldn't just do a level skipper or infinite lives like you would a shooter or a platform game, you physically had to play it, and the nature of the game meant that could be days to complete it, which is what made the protection effective. |
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21 January 2020, 16:09 | #248 |
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Isn't it basically impossible to prevent cracking on a system like the Amiga where you can more or less read out everything in memory at 'all times'?
I'd say your best bet to prevent cracking would be to try and somehow create code that will always hang/crash/fail any debugging attempts (i.e. block Action Replay and similar hard/software solutions, make it so a reset is either impossible or will wipe memory, etc). And even if this would be possible to do with a 100% success rate (which it may not be), I'm still fully unconvinced you can actually stop cracking that way. |
21 January 2020, 16:18 | #249 |
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As long as you have full control over the machine, you can't prevent cracking. For example, if you take games like Diablo 3, it's quite different, because part of the code is not even on your machine, so if done right, this can prevent cracking, because you don't have the whole code available for analyzing.
On any machine, where you get the full code physically (discs, cd, etc.) you can not prevent this. I'm not sure if a dongle could prevent this. It probably depends. Theorethically you could send it all kind of inputs and look at the output, so I think this wouldn't be safe either. |
23 January 2020, 05:09 | #250 |
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03 March 2020, 08:26 | #251 | |
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Yeah and those were well hidden in odd places as well, such as a routine that buffered mouse clicks (eg when "running", ie clicking on the forward arrow repeatedly and quickly so that the gfx couldn't keep up), after the fifth or so click the check kicked in... |
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03 March 2020, 08:50 | #252 | |
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Also these checks can be removed. Besides, not everyone used cartridges for cracking, how do you want to detect if someone just looks at the code using a plain old disassembler for example? |
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03 March 2020, 08:56 | #253 | |
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The loader was encrypted with a trace vector decoder. That's the only place I saw one of those outside of CopyLock, but it was a simpler variant that used fixed instruction lengths instead of a table. It also had quite a few checksums, as you say, and manual protection. Tricky enough Last edited by girv; 03 March 2020 at 10:08. |
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03 March 2020, 09:01 | #254 |
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Treasure Trap's protection also used the Trace Vector idea just like Copylock. It was a much simpler TVD than late Copylocks though and, even worse, nothing was hidden in the encrypted code which made the protection quite weak. |
03 March 2020, 09:47 | #255 | |
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but often crackers used dump of memory after main code decryption... however there was still as you indicated the problem of very long tracks ($19e0 with control data) more complicate for whdload's patch because we must decrypt data and not just copy on disk decrypted data (in my memory Dragons lair 1 need many works to decrypt properly main code and recently Vortex but more simple) some protections seem complicate to crack but often only skip first encrypted loader to crack it (recently Chinease Karate or Albedo encypted boot) recently, i found the more stupid protection with Wrangler (http://www.whdload.de/games/Wrangler.html) it's an external file named 'T' file 'T' is really simple, it test a long track and crash the OS if no success. In my memory by: move.l 4 ,a0 jmp (a0) you have just to launch main code directly to crack game... it'seems there no another protection test in main code... Last edited by CFou!; 03 March 2020 at 16:47. |
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03 March 2020, 12:23 | #256 | |
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Same as in Cougar Force, protection code is in an external file ("loader") which is executed in the startup-sequence. "Cracking" just requires removing the "loader" line from the startup-sequence. |
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03 March 2020, 21:48 | #257 | |
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I wonder how many early Amiga games were this badly protected? |
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03 March 2020, 21:51 | #258 |
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every time the main development team isn't involved with the protection and it's added afterwards.
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06 March 2020, 17:47 | #259 |
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07 March 2020, 14:58 | #260 | |
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