Cracking Apple II floppy copy-protection - 4am

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lurkio
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Cracking Apple II floppy copy-protection - 4am

Post by lurkio » Sun Jun 17, 2018 6:41 pm

Interesting interview with "4am", a prolific cracker of Apple II floppy disk copy-protection (of which there seems to have been a surprising variety of different methods):
:idea:
Last edited by lurkio on Sun Jun 17, 2018 10:32 pm, edited 3 times in total.

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BigEd
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Re: Cracking Apple II floppy copy-protection - 4am

Post by BigEd » Sun Jun 17, 2018 7:35 pm

Excellent find!

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Lardo Boffin
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Re: Cracking Apple II floppy copy-protection - 4am

Post by Lardo Boffin » Sun Jun 17, 2018 9:40 pm

Really interesting read!
BBC model B 32k issue 4, 16k sideways RAM, Watford 12 ROM board, Viglen twin 40/80 5.25" discs, Acorn 6502 coproc
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leenew
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Re: Cracking Apple II floppy copy-protection - 4am

Post by leenew » Sun Jun 17, 2018 10:46 pm

Very interesting read.
Thanks :D

Lee.

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davidb
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Re: Cracking Apple II floppy copy-protection - 4am

Post by davidb » Sun Jun 17, 2018 11:49 pm

Thanks for posting the link. It's very interesting to read 4am's perspective on copy protection.

I wonder if the Scott Adams adventures on Acorn platforms had similar in-game copy protection checks to those mentioned in the interview. I don't think I've ever looked at those games in any detail. Does anyone know?

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BigEd
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Re: Cracking Apple II floppy copy-protection - 4am

Post by BigEd » Sun Jun 17, 2018 11:54 pm

Some, or many, of the 4am cracks as found on the Internet Archive have a commentary of the cracking process - it's worth reading at least one or two of those.

See the *.txt file in the Show All catalogue of each title:
https://archive.org/download/MathBlaster4amCrack

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BigEd
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Re: Cracking Apple II floppy copy-protection - 4am

Post by BigEd » Tue Jun 19, 2018 7:24 pm

It turns out 4am has tweeted some highlights of especially interesting cracks:
https://twitter.com/a2_4am/status/993129396520341504

Burger Time and Mr Do are among them.

The Apple is special because the disk interface does so very little - so much is done in software and therefore ripe for customisation and exploitation. Also, the disk drive itself has an AGC such that more than two bit-times without a flux transition causes a progressive gain increase which eventually returns noise. Because of the very low-level interface, this "feature" can be used as a means to detect copies. Similarly, all the sector markers and other metadata values can be manipulated under software control, and even the stepper motor is manually driven at a quarter-track resolution, allowing spiral tracks to be recorded and read back - if you can step by the right amount at the right time. More here.

(via https://www.metafilter.com/156086/Prese ... -at-a-time)

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Re: Cracking Apple II floppy copy-protection - 4am

Post by Cosmo » Wed Aug 08, 2018 11:11 am

Search from youtube "kansasfest" and you'll find some videos where he presents his auto-cracking software, "Passport" and much more.
Excellent stuff, great guy.
Acorn BBC Master w/Datacentre & PiTubeDirect, BBC Micro Model B Issue 7 w/Gotek
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