Questions tagged [copy-protection]

For questions about copy protection techniques used on retro software.

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2
votes
2answers
1k views

Why does changing a DOS/Windows EXE cause it to not run? [closed]

If I hex-edit an EXE for DOS or Windows, by adding or removing some text for example, it will no longer run. If I just change a single char around to a different one, it may run. Is this some anti-...
3
votes
1answer
160 views

Where can this "boot.B" file be coming from on this Spectrum TR-DOS disk image?

After working on some tools that parse the TR-DOS disk image format .TRD files for a while I just noticed that one of the game disk images I had downloaded "La Abadia Del Crimen", only has three files ...
6
votes
1answer
482 views

What is the Nintendo 64 IPL3 and how could it be created by Rust developers?

I was delighted to learn there is an integrated toolchain for Rust development that supports the Nintendo 64. According to the documentation: For copyright purposes, the IPL3 binary is not included ...
3
votes
3answers
467 views

Pirated spreadsheet software introducing intentional errors?

Was there ever a case of a spreadsheet application introducing intentional floating-point errors when it detected that it had been pirated? Particularly errors that were small enough to go unnoticed ...
10
votes
6answers
2k views

Copying tapes "back in the day"

Back when I had a ZX Spectrum 48K, I had a friend that had a 128K and we would swap games for the weekend from time to time. We did try and make duplicates of the tapes (yes, I know, but we were ten ...
40
votes
3answers
4k views

How did Apple II BASIC programs protect against listing?

I seem to recall from my high-school days that certain Apple II programs protected themselves from being listed and therefore modified. If you tried to do it, the machine would simply reboot. How did ...
12
votes
2answers
2k views

Weak bits on floppy for copy protection

How did the vendors using copy protection create weak bits on the floppies? This always fascinated me as a kid. I ended up finding a weak bit emulator that would intercept the floppy disk interrupt ...
4
votes
3answers
1k views

How can I view BASIC code hidden by SYS?

I ran a validation of an old disk, and it turns out this ruined a game (won't load) and deleted my old high score list on David's Midnight Magic. I would like to edit the code to get the high score ...
5
votes
0answers
420 views

Rainbow Technologies Ltd DRM system for DOS

A number of games from the early 1990s appear to be protected with a DRM system developed by Rainbow Technologies Ltd. The system allows content in the games to be unlocked by sending the manufacturer ...
10
votes
4answers
887 views

Was the Amstrad's file protection considered secure in 1985?

I just reverse engineered the file protection on the Amstrad CPC, which uses two sequences of rotating bytes taken straight out of the AMSDOS ROM to XOR each byte of the file. If you have SEQa of 13 ...
12
votes
2answers
1k views

How was Prince of Persia "better/faster" with RWTS18?

I was reading about Prince of Persia over at POP Code Review. In that article, the writer printed an interview with Roland Gustafsson, the inventor of RWTS18 copy protection for the Apple II series. ...
8
votes
3answers
813 views

Advantages to installing a parallel port in a C1541-family drive other than speed

Are there any advantages to installing a parallel port in a C1541-family drive and using a parallel cable to a PC to image disks, other than increased speed (i.e. since the standard IEC protocol is ...
21
votes
3answers
2k views

How did "full memory" Spectrum tape copiers work?

There are some tape copiers, such as LERM that claim to be able to copy tapes which contain software that takes the full 48kbyte of RAM. However, this seems impossible on a Spectrum, when the whole ...
30
votes
1answer
1k views

How does "bit-slip" copy protection work?

Some Apple II 5.25" floppies used a special pattern of bytes that could not be automatically detected by disk copying software. How could the pattern be invisible to disk copiers but detectable by ...