Double Dragon 2

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Category: TutorialsAmigaCrackingMFM
Author: Phantasm
Submitted by: musashi9
Date: 2014-08-04 14:49
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Phantasm 2014!
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FileDownload: Double Dragon 2
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2014-08-05 01:05

1. Wack0 writes

I guess I'm going to have to leave the message here that Richard Aplin left in Final Fight, since it refers to the protection of this game somewhat!
Reply to comment #1
2014-08-05 13:31

2. Bilbs writes

I've never seen that before - it's bonkers :)
2014-08-05 11:30

3. WayneK writes

Fantastic work Phantasm, I know how much effort must go into producing a tutorial like this! As you said, I'm surprised there were no "modified memory" checks when you consider how much work was put into encrypting/hiding loaders etc... I remember Stingray teaching me about the copperlist blitter-decrypt stuff many years ago - very clever method! Can you think of any other games that do similar?
Reply to comment #3
2014-08-06 09:01

4. Phantasm writes

given that the data is mixed in with the code and not separated out i guess any checksums would have to be quite targeted (otherwise data/variables that might change would end up affecting the checksum results). Also the checksums would have to be careful to only be executed when the encrypted/decrypted areas of memory were in a known configuration. As for the copperlist/blitter decrypt stuff I haven't seen that in action before although I was aware of the idea. This one did have some neat ideas and was a fun project. It could have been made much more painful if each of the encrypted files used a different key that was passed into the loader. It would then have made it necessary to go find all the decryption keys.
2014-08-06 20:16

5. scenex writes

Thanks a lot for providing a tutorial on a title, which is considered, to my knowledge, as one of the best protected Amiga games ever written!
2014-08-08 11:32

6. aLpHa oNe writes

I am really impressed how heavy things can be protected. Thanks for the tutorial although it's hard for me to follow. :-) Great work and respect for your skills.
2014-08-19 23:43

7. dlfrsilver writes

Wow, congratulations Phantasm for doing such a great tutorial like this. Incredible all the protections encountered so far, and the mess it is to remove/patch them all !!!
2014-09-19 02:46

8. plagueis writes

Excellent! Thanks Phantasm, this was highly educational. I'll be saving this to keep among my references.
2014-09-30 22:15

9. Richard Aplin writes

Super entertaining! Thanks! I'd forgotten most of the protection stuff I put in there but I do remember taking some time and having some fun with it. Yeah hiding decryption keys for each file somewhere would've been a good one, but only so many hours in the day... As you can imagine, making all that protection code actually work in the first place was quite time-consuming. I think it took a week or two to do. Thanks so much, a great blast from my past :-) Rich
Reply to comment #9
2014-10-03 16:05

10. phantasm writes

glad you enjoyed reading it. its pretty amazing that there are still people out there that are interested in reading this stuff (and writing it too). It was fun writing this too and it took me back to the old days :-)
2016-06-07 22:03

11. TheSpecialist writes

Wow I never figured Amiga protections where this tough ! I've been reading how some hackers did 3 cracks in day, that would be impossible with this one it seems to me. Very nice copper/blitter idea indeed. Who was the first one to crack this and anyone any idea how much time it took him ?
Reply to comment #11
2016-06-09 11:08

12. Phantasm writes

I can't believe its close to two years since I wrote this tutorial - maybe its time i started on a new one.
Reply to comment #12
2016-06-10 19:06

13. thespecialist writes

Parasol stars is supposed to be relatively difficult. I read that it took them a week to crack Double Dragon 2, which seems about right I think. It's a relatively difficult protection but of course easy compared to modern protections like we have now (difficult now could mean weeks if not months of work while difficult on the Amiga meant days). BTW I've sent you a PM mate !
Reply to comment #13
2016-06-13 15:34

14. Phantasm writes

i'll take a look when i've got some time. I'm not sure that a tutorial around spending days bypassing various levels of encryption and hunting down checksums is going to be that interesting to write (or read for that matter). I tend to favor the MFM stuff as I find that more fun to work with.
Reply to comment #12
2016-06-10 10:43

15. scenex writes

Sounds like a great idea indeed :)
2016-06-14 10:51

16. Sunny writes

Hi, I thought I would just put a couple out there. Shinobi looks very similar(maybe identical) to this one. I cant seem to find out how it manages to disable AR3 though (Apparently very easily no doubt?) Also has an interesting anti piracy pic when copy loaded. Another one is Fire&Ice, disk 1 appears to have a copylock-type on track 0, and then tracks 65-80 seem to have some MFM encoding??? I think it uses the copylock for its encrypted bootblock?, but you can easily copy out decrypted bootblock at 59e8 after track 1 loads. This will enable the disk to load to around track 19/20 where it will keep asking/checking for program disk? Disk 2 has no protection.