12 January 2023, 22:08 | #1 |
Registered User
Join Date: Jan 2023
Location: Denmark
Posts: 36
|
Why not complete MFM decoder in boot block?
Dear all =)
I have just read how to crack Street Fighter 2 at https://securityimpact.files.wordpre...protection.pdf where I don't understand why the boot block doesn't contain the complete MFM decoder. Given X-Copy only can read the boot block, then I would expect that the MFM loader and decoder is in the boot block? But on page 14 he explains how he let's the game decode the data, where I would have expected this decoder must be in the boot block, because how could the boot block other read those tracks? Can someone explain what I am missing? Hugs, Sandra =) |
12 January 2023, 22:17 | #2 |
move.l #$c0ff33,throat
Join Date: Dec 2005
Location: Berlin/Joymoney
Posts: 6,863
|
Just had a (very) quick look, the MFM decoder is in the bootblock at offset $28c.
|
12 January 2023, 22:23 | #3 |
Registered User
Join Date: Jan 2023
Location: Denmark
Posts: 36
|
|
12 January 2023, 22:24 | #4 |
move.l #$c0ff33,throat
Join Date: Dec 2005
Location: Berlin/Joymoney
Posts: 6,863
|
I did not check the tutorial, I would have simply used the MFM decoder from the bootblock to rip the disks and then worked with the images.
|
12 January 2023, 22:26 | #5 |
Registered User
Join Date: Jan 2023
Location: Denmark
Posts: 36
|
|
12 January 2023, 22:29 | #6 |
move.l #$c0ff33,throat
Join Date: Dec 2005
Location: Berlin/Joymoney
Posts: 6,863
|
My pleasure.
|
12 January 2023, 23:52 | #7 |
Moderator
Join Date: Nov 2004
Location: Eksjö / Sweden
Posts: 5,602
|
Why questions tend to get speculative answers.
On Amiga, a complete MFM loader fits in the bootblock. Copy protection ideas are a reason why a game wouldn't hand a cracker a complete loader in the bootblock. Not all MFM loaders released fit in a bootblock. Some coders optimize better/worse than others. |
12 January 2023, 23:57 | #8 | |
Registered User
Join Date: Jan 2023
Location: Denmark
Posts: 36
|
Quote:
Would that be possible? |
|
13 January 2023, 00:08 | #9 |
move.l #$c0ff33,throat
Join Date: Dec 2005
Location: Berlin/Joymoney
Posts: 6,863
|
Yes, such games exist. Multiple SYNCs, completely different track formats (different track length/encoding and more) etc. pp.
Edit: Yogi's Big Clean Up is such a game for example: http://www.whdload.de/games/YogisBigCleanUp.html Last edited by StingRay; 13 January 2023 at 00:15. Reason: Added example game |
13 January 2023, 00:57 | #10 | |
Registered User
Join Date: Jan 2023
Location: Denmark
Posts: 36
|
Quote:
|
|
25 January 2023, 05:14 | #11 |
Registered User
Join Date: May 2015
Location: Australia
Posts: 131
|
Ironically X-Copy was used to crack and copy disks but it was commercial software. I have a disk with X-Copy that also includes other tools for disk cracking. Some allowed to map the whole disk with different MFM codes. That way disks could be copied. This would circumvent a static copier that only knew DOS format.
Aside from adding extra drive support I would have thought using a tool to map MFM codes would be easier. Then just duplicate it at will once the MFM codes are known. Of course if the disk has specific corruption on sectors that can break. In any case no amount of copy protection can ignore the obvious back door in all bootable disks. The boot block. The boot block cannot be encrypted and so makes every boot block a back door. The code is plain. Just read through it and see how it sets up disk registers. Then follow it to the next routine. Having a live debugger like Action Replay helps. But anything thing where boot code can be loaded in will do. Can even execute it. Keeping in mind it tends to run in supervisor mode. |
25 January 2023, 08:13 | #12 | ||
Registered User
Join Date: Mar 2018
Location: Hastings, New Zealand
Posts: 2,544
|
Quote:
Quote:
Problem is some people had more fun cracking games than playing them, then were 'obliged' to distribute pirate copies to increase their 'street cred'. If they just cracked disks for their own use it wouldn't have been so bad, and software developers wouldn't have had to apply more and more sophisticated protection schemes. The real damage wasn't done by the crackers, but by the unscrupulous pirates who were just in it for the money (including users who didn't want to pay for genuine software - not understanding that they were part of the reason it was so expensive). |
||
25 January 2023, 09:00 | #13 | |
CaptainM68K-SPS France
|
Quote:
Look when the CDROM appeared 'we will make the prices lower'. Bullshit ! They rised up the prices even higher ! |
|
25 January 2023, 14:31 | #14 | |||
Registered User
Join Date: May 2015
Location: Australia
Posts: 131
|
Quote:
LOL. I had it given to me on disk years ago. I only found out it was commercial a few years back. Quote:
I used to spend time cracking games for my own use. Or hacking as I called it. If I found it too difficult to play I spent time looking for cheat codes in code, analysing keyboard routines and looking for life counters as a last resort. I had a selectable 512KB expansion I used as a poor mans Action replay. Load a game, reboot and disable, examine code locked in the 512KB, Quote:
I had a few games shared to me. I also loaned my Test Drive II to a school friend I didn't see again. Cost me $50 so I rather angry at that one. Later I found another at a local computer shop in my local shopping centre for $10 bucks and must have bought 5 boxes of games that day. Or was it ten? TD II was different somehow. The shop is gone years ago, but I still know where it used to be. |
|||
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests) | |
Thread Tools | |
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
SPS Decoder Library 5.1 (formerly IPF Decoder Lib) Windows binary + source released | mr.vince | News | 29 | 08 February 2021 03:46 |
A1200: Error reading boot block on Gotek | PortuguesePilot | support.Hardware | 5 | 02 June 2017 02:01 |
Boot block examples? | h0ffman | Coders. General | 3 | 04 March 2011 16:44 |
Why can't I open the Topaz-font in a boot block? | Leffmann | Coders. General | 13 | 19 May 2010 21:52 |
GAMES: 1) impossible to complete, 2) almost completed, 3) you will complete | adamst85 | Retrogaming General Discussion | 33 | 28 November 2004 14:30 |
|
|