Floppy Disk Copy protection

[DrCoolZic]

I am just restarting a new thread on this subject the old one started more than 5 years ago (http://www.atari-forum.com/viewtopic.php?f=47&t=9012) is hard to follow because I have written a lot of incorrect things at the time

I think that now I have a better understanding of the protection mechanisms used on Atari. You will find attached the new version (version 1.0 ) of my document on protection.
Please feel free to give feedback.

____________________________________________________________________________________________________________________________
EDIT November 9, 2014
You can find complementary information about Atari copy Protection/Preservation @ http://info-coach.fr/atari/software/preservation.php
This will also point you to the latest version of the document at http://info-coach.fr/atari/documents/_m ... ection.pdf
____________________________________________________________________________________________________________________________

[DrCoolZic]

Time for a new version

This new version is a major rewrite. It includes a lot of new protections like Fuzzy Data Track, unformatted and partially unformated track, more info on NFA, lots of new description for games, detail explanation on unformatted track, NFA etc...
Still needs more work especially in the Analysis of Games/Programs section

However I beehive it contains a lot of useful information

[troed]

However I beehive it contains a lot of useful information

Many thanks for an interesting read.

/ex-cracker who never knew how the actual disc protections were made. Just how to cancel them out

[bandit]

holy poo! A very nice document!!!

[dlfrsilver]

Time for a new version

This new version is a major rewrite. It includes a lot of new protections like Fuzzy Data Track, unformatted and partially unformated track, more info on NFA, lots of new description for games, detail explanation on unformatted track, NFA etc...
Still needs more work especially in the Analysis of Games/Programs section

However I beehive it contains a lot of useful information

Jean-Louis, Maupiti Islands, Obitus, Golden Axe are all using amiga tracks as protection. Remember Aufit reporting the tracks as Amiga ones ?

[AtariZoll]

...
Jean-Louis, Maupiti Islands, Obitus, Golden Axe are all using amiga tracks as protection. Remember Aufit reporting the tracks as Amiga ones ?

Is there something really specific in Amiga floppy tracks ?

[dlfrsilver]

...
Jean-Louis, Maupiti Islands, Obitus, Golden Axe are all using amiga tracks as protection. Remember Aufit reporting the tracks as Amiga ones ?

Is there something really specific in Amiga floppy tracks ?

Yes those tracks are written in amiga format. Aufit detects those tracks, and they are seen as amiga tracks, they are mostly one big tracks with 1 sector per track.

[DrCoolZic]

I call those tracks "No Sector Data Track" and they are described page 17.
I need to find a better name!
This cover Amiga tracks but also other kind of tracks ....

[AtariZoll]

Of course that there is no "one big sector" in such tracks. Also, it is wrong to call it Amiga format, just because track read is normal Amiga way of floppy access.
We can call it: tracks without regular sectors, raw track data, or just track read

[Codetapper]

Time for a new version

This new version is a major rewrite. It includes a lot of new protections like Fuzzy Data Track, unformatted and partially unformated track, more info on NFA, lots of new description for games, detail explanation on unformatted track, NFA etc...
Still needs more work especially in the Analysis of Games/Programs section

However I beehive it contains a lot of useful information

If you ever update the document again, can you please change the broken link for the Rob Northen interview to the page on codetapper.com (which should stay forever) as it looks like tripod has shut down my account or something

[DrCoolZic]

Time for a new version

This new version is a major rewrite. It includes a lot of new protections like Fuzzy Data Track, unformatted and partially unformated track, more info on NFA, lots of new description for games, detail explanation on unformatted track, NFA etc...
Still needs more work especially in the Analysis of Games/Programs section

However I beehive it contains a lot of useful information

If you ever update the document again, can you please change the broken link for the Rob Northen interview to the page on codetapper.com (which should stay forever) as it looks like tripod has shut down my account or something

done

[DrCoolZic]

New version 1.3 of the Atari FD protection document.

Lot of work !!!

- Added detail analysis of protections on many new games that have been discussed recently on Atari Forum. Including ECO, Golden Axe, Jupiter Masterdrive, Maupiti Island, Obitus, Time of Lore, Vroom, Wizball, Z-out ...
- Now protection are grouped into two categories: data prot / timing prot
- Added Fuzzy track prot
- More details on Invalid ID field
- More details on shifted tracks
- Added write splice, Sync mark descriptions
- Chapter on preservation
- fixed lot of errors + clarification
...

document is too big to be uploaded (about 7MB) so directly available at http://info-coach.fr/atari/documents/_m ... ection.pdf

Feedback welcome

[DrCoolZic]

Sorry I messed up during word to pdf conversion and the hyperlinks were not converted properly
Problem is now fixed you should be able to get a working version following the original link. http://info-coach.fr/atari/documents/_m ... ection.pdf

Internal hyperlinks should now work. Tested with Acrobat reader and Pro as well as Chrome / Firefox and IE
Be aware that many browsers use cache for recently visited documents so you may need to do a refresh.
The document should now show version 1.3a

[Maartau]

[DrCoolZic]

I have just received questions about preservation / backup of floppies. This is obviously related to protections as key disk makes these operations harder to do.

Therefore I have updated my page on Preservation / Backup http://info-coach.fr/atari/software/preservation.php where I compare several preservation techniques/hardware ...
I have tried to be as impartial as possible about the different HW vendors DC / FK / SCP / HxC / CE
So let me know what you think and if you feel I should update

[Brume]

A quick message to let you know we created a new forum under DrCoolZic's request (nice idea!).

So, all topics mainly devoted to copy/preservation are now located in the Floppy Disk Copy protection forum.

Of course, KryoFlux, SuperCard Pro & Pasti forums are still alive.

Thanks for reading (I told you it would be quick!).

[DrCoolZic]

New version 1.4 of my Atari Floppy Disk Copy Protection document

Lots of information about the WD1772 has been added + fixes and new game analysis
Detail:

Beyond many small fixes in text the following sections have been added:
- Sector with No Data (SND) protection,
- WD1772 MFM track language,
- WD1772 Synchronization (sync marks detection),
- WD1772 False sync mark detection,
- WD1772 Bug in Read/Write Track commands,
- WD1772 CRC Information,
- Special case of No Flux Area over index,
- Hidden data.
The Sync Mark in Data (SMD) protection has been removed.
Analysis of Dragon flight game has been added.

Document is 7MB so get it directly from my web site at
http://info-coach.fr/atari/documents/_m ... ection.pdf
from page http://info-coach.fr/atari/documents/myDoc.php

[Hawk78]

Wow! Very interesting to read. I didn't expect so many different protection types.
Now it's clear to me why so many games have been cracked...

Do you think it's possible to create the "ultimate copy machine" which consists of an affordable hardware (floppy-)drive which can reproduce all those protections you mentioned?

[dlfrsilver]

There are many, one of which is Kryoflux It allows to preserve original games, and also writing them back (thru IPF files).

[JimDrew]

Another is SuperCard Pro, which lets you create images for use in various computer emulations (Atari, Amiga, BBC, etc.) and also lets you write the image back to a real disk.

[DrCoolZic]

Another sollution but hard to find nowadays is the Discovery Cartridge from Happy Computer

Unfortunately the company is long time gone but this HW allows to copy copy protected diskette directly on an Atari
http://info-coach.fr/atari/hardware/devices/dc.php

While backing up originals to floppies still make sense it is harder and harder to find a diskette in good condition to backup your original
You should therefore also consider to use HW emulator on an Atari like HxC2001 http://hxc2001.free.fr/floppy_drive_emulator/ or CosmosEx http://joo.kie.sk/?page_id=384 (limited image support currently) - using images created with KryoFlux or Supercard Pro.
Other alternative is of course to use SW emulators

[Hawk78]

...okay but how can you handle those "WeakBit" Protections (Section 4.11.3)?

Those tracks will return random bits everytime they will be read. How will you identify the track path for correct duplication?

WeakBit-Track.PNG

Even if you read "normal" tracks again and again and it shows you differences you don't know if it's a random read error or part of the protection...

[DrCoolZic]

Weak bits in 4.11.3 are presented for reference as they are described in patent "US Patent 4,849,836 *** Copy Protection for Computer Disks - Used in Dungeon Master, Chaos Strike Back ...." *** http://info-coach.fr/atari/documents/ge ... 849836.pdf found in page http://info-coach.fr/atari/software/pro ... references
As described in the pattent these are real "Weak bits" (as they produce weak signal) that results in fuzzy bits.

But the weak bits described in Fig 3, 4, and 5 are not used on Atari as far as I know. What is used is what is described in Fig 1 & 2 (used in Dungeon Master, Chaos Strike back). However, if they existed, they could be imaged with Kryoflux and Supercard Pro and they would result in fuzzy bits as long as you image SEVERAL revolutions and compare the bit values.

[Steven Seagal]

Weak bits in 4.11.3 are presented for reference as they are described in patent "US Patent 4,849,836 *** Copy Protection for Computer Disks - Used in Dungeon Master, Chaos Strike Back ...." *** http://info-coach.fr/atari/documents/ge ... 849836.pdf found in page http://info-coach.fr/atari/software/pro ... references
As described in the pattent these are real "Weak bits" (as they produce weak signal) that results in fuzzy bits.

I also have doubts about this patent being for Dungeon Master. What they do seemed to be different when I read it, but maybe I misunderstood, can't explain the differences from memory, just that I removed the reference in Steem doc.

[JimDrew]

"Fuzzy bits" is not exactly the same thing as REAL weakbits. This is what I have been trying to convey for awhile. That Dungeon Master protection relies on the fact that valid bitcell durations are written that cross the boundary of what the FDC accepts as valid data for each of the possible (3) different timing windows. Because the disk is rotating, the bitcells are deliberately not the same duration between groups, and the FDC's clock is much faster than the rotational speed of the disk, each time data is read it will change - but the value of ALL of the bitcells times fall within the 4us-8us window. REAL weakbits, where the bitcell time is random every single time you read it, will have values that dip below and above the data separator's clocking window - which is a single window that encompasses much more time. When the data separator's clocking window is exceeded, whatever time is in the clocking timer is output. This is conjunction with the data separator turning up the AGC to try to fix the issue adds to the randomness, but since we have N/S poles it is balanced.

REAL weakbits can in fact be determined using a single revolution. This is accomplished by looking at consecutive bitcells. There is an interesting byproduct of the how the data separator works on floppy drives - if you add up all of the bitcell times of the weakbits they will equal the same amount of time that you would have for normal data. So, you can scan through and see which bits are outside of the FDC's normal 10% clocking window and then draw a comparison to the surrounding bitcells and mark anything outside of the range as a weakbit, and typically (especially with C64 protections) you can tie together any bitcells that appear to be valid (within the total amount of space allowed for bitcells - ie 4us-8us) that are within a series of invalid bitcells. Remember, we are dealing with N/S poles with flux too so weakbits typically come as pairs.

Because the bitcells times all add up to be the same length as normal data, the track length doesn't fluctuate much (if at all), and that is why we can write back a weakbit protection using just a single revolution of capture. If an emulation simulates the rotation of the disk, the length of the flux data likely will not come out perfectly so that track repeats the exact same data. WinUAE's data separator emulation just clocks in the data at the correct sampling rate, using the raw flux data and since the flux data was captured on a drive and has the same drive speed "wobble" that a real drive would, that jitter is automatically introduced. WinUAE can load anything with weakbit protections without having to do anything special, just clocking in the data, and only using an image that contains a single revolution.