Jolly Jack Tar by Sherston Software, original protected disc

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scarybeasts
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Jolly Jack Tar by Sherston Software, original protected disc

Post by scarybeasts » Sat Sep 12, 2020 11:34 pm

Hi,

Courtesy of billcarr and discbeast, please find attached image in HFE format.

It's a less common title, and also has a relatively unusual (and powerful!) disc protection. If the copy protection fails, you might get a screen like this:

western_sec_fail.png

The protection is very interesting in that it detects if the beeb has an 8271 or 1770 and uses a divergent copy protection check(!) This HFE is the first one that works on both 8271 and 1770 systems.

This disc may well have been written to after the initial duplication. The "score" and "rec" files possibly. Part of the history I guess :)

This disc is also one of those that appears to have fragments of the mastering program on it, albeit corrupted (ignore the byte indexes):

6080: 0D 04 4E 05 F4 0D E4 3C 06 20 DB 0D E4 3D 26 20 ..N....<. ...=&
6090: F1 22 43 48 4F 4F 53 45 20 50 52 4F 47 52 41 4D ."CHOOSE PROGRAM
60A0: 00 2F 4E 44 20 34 30 2F 38 30 20 54 52 41 43 4B ./ND 40/80 TRACK
60B0: 22 0D E4 43 13 20 E3 20 58 20 3D 20 31 20 B8 20 "..C. . X = 1 .

5C80: 20 61 6E 6F 74 68 65 72 2C 00 33 53 43 20 54 5D another,.3SC T]
5C90: 20 45 5C 64 22 0D 02 AF 0A 20 D2 45 41 49 54 0D E\d".... .EAIT.
5CA0: 02 B0 1D 20 DB 3A F1 22 57 72 69 74 69 6E 67 20 ... .:."Writing
5CB0: 66 69 6E 47 53 72 70 72 69 6E 74 22 0D 02 B1 22 finGSrprint"..."

I have suspicions on what "fingerprint" may apply to, given how the protection appears to work. It's possibly ingenious, I may have to write up a blog post.


Cheers
Chris
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BigEd
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Re: Jolly Jack Tar by Sherston Software, original protected disc

Post by BigEd » Sun Sep 13, 2020 8:13 am

Oh, please do write up the protection method! (And, I think you said you'd write up how you managed to do arbitrary and sufficient reads and writes with the 1770? Or maybe you have, but I've missed it?)

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scarybeasts
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Re: Jolly Jack Tar by Sherston Software, original protected disc

Post by scarybeasts » Sun Sep 13, 2020 8:22 am

BigEd wrote:
Sun Sep 13, 2020 8:13 am
Oh, please do write up the protection method!
Ok, I can commit to doing so. I want to get my hands on a few more disc samples (ideally duplicates of the same title) first, to get more clues.
(And, I think you said you'd write up how you managed to do arbitrary and sufficient reads and writes with the 1770? Or maybe you have, but I've missed it?)
I just volunteered to talk at the October vABUG on discbeast, archiving and variants. I can certainly cover the 1770 trick then if you don't mind waiting a few weeks?


Cheers
Chris

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BigEd
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Re: Jolly Jack Tar by Sherston Software, original protected disc

Post by BigEd » Sun Sep 13, 2020 8:30 am

Excellent! I'm happy to wait for a couple of weeks - easiest job in the world!

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