Protection systems

Hardware Hacking, Programming and Game Solutions/Cheats
Sarah
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Re: Protection systems

Post by Sarah » Thu Sep 03, 2015 8:18 pm

The vast majority of tape based software used standard block structures, even if (as mentioned above) some of the more interesting loaders utilised various non-standard / out-of-order block types or deliberate CRCs, etc. As a result, close to 100% could be copied reliably and fairly easily with Quickbeam's Duplicas 5, since it was capable of reproducing nearly all such variations.

I'm not entirely sure that Design Design's releases were amongst the few exceptions and can't easily check but I do remember studying the code and being impressed (pretty much baffled) by the amount of processing it managed to perform during the time between those seemingly continuous 32 byte blocks, to achieve that backwards scrolling effect without resulting in an ?IO ERROR. It wasn't gapped (unlike some of Microdeal's releases that unnecessarily had both gaps and full leaders inbetween every block & consequently took ages to load). If there's extra data in there before the SYNC, I can't see it doing any harm, so I think surely wouldn't be there to defeat tape-to-tape attempts; I'd be more likely to bet on it being either accidental or a 'spacer' to help mitigate the aforementioned processing overhead.

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robcfg
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Re: Protection systems

Post by robcfg » Fri Sep 04, 2015 5:18 pm

You were right, guys!

I removed the ghost pulses and added sync bytes to fill the big gap before Rommel's Revenge loading screen and now I can load it both on XRoar and a real Dragon.

The zipped cas file is now updated.

Thanks so much!

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tormod
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Re: Protection systems

Post by tormod » Sun Sep 06, 2015 1:11 pm

Fantastic, Rob! Looking much forward to your tape recovery tool. When I pulled down the Dragon from the attic some 2.5 year ago it was for recovering my old programs from tape. And some of them failed to load, but then I got severely distracted by all other Dragon projects, so I need to get back to this and your tool looks like exactly what I need.

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robcfg
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Re: Protection systems

Post by robcfg » Sun Sep 06, 2015 10:35 pm

I updated the Tube Way Army cas file, which now loads both on XRoar and on a real Dragon.

I'll be opening a new post soon regarding my new tool. Meanwhile, which OS do you guys normally use? I'm finishing a couple of things, and as soon as they are ready, I'd like to release some binaries for you to test. I'll be releasing the source code once I clean and refactor it a bit.

sorchard
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Re: Protection systems

Post by sorchard » Mon Sep 07, 2015 8:20 am

robcfg wrote:which OS do you guys normally use?
I mainly use WinXP 32 bit at home. Also Win7 64 bit, though the same 32 bit binary should work fine on both.
Stew

zephyr
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Re: Protection systems

Post by zephyr » Mon Sep 07, 2015 3:16 pm

sorchard wrote:
robcfg wrote:which OS do you guys normally use?
I mainly use WinXP 32 bit at home.
I will be using only WinXP Pro 32 bit for at least the next several years.

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tormod
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Re: Protection systems

Post by tormod » Thu Sep 10, 2015 9:55 pm

I normally use 64-bit Linux, but also have 32-bit to test on (and multi-arch libraries to make it run on 64-bit anyway).

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robcfg
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Re: Protection systems

Post by robcfg » Thu Jun 09, 2016 11:42 am

Hello guys!

I was dumping "And All Because..." and noticed that it loaded from the wav file but not from the cas file despite being correct.

So I took a deeper look, and the tape has a basic program followed by some empty room, and then the graphics data. The program is made so that when you select difficulty and press enter, it turns the motor on, makes a 1500 iterations empty for bucle and after that a CLOADM.

If you skip the empty room on the tape, the program will fail to load.

Can this be considered a protection scheme?

Sarah
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Re: Protection systems

Post by Sarah » Wed Feb 22, 2017 8:23 pm

Just the motor running on and the start of the binary part being missed, if the gap is insufficient, I presume? That wouldn't present much of a challenge to someone attempting to copy it. The "" file in the archive appears to be a rip that I made long ago, so would've been tested and verified working on T3 at the time. Were you dumping an original cassette -- maybe this was the game that had some music recorded on the tape, which it tried to play out with AUDIO ON?

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