Log inRegister an accountBrowse CSDbHelp & documentationFacts & StatisticsThe forumsAvailable RSS-feeds on CSDbSupport CSDb Commodore 64 Scene Database
You are not logged in - nap
CSDb User Forums


Forums > CSDb Discussions > Laurin disk "encryption" broken
2016-03-30 21:39
Ymgve

Registered: May 2002
Posts: 84
Laurin disk "encryption" broken

I did a little research after hearing about the Laurin disk encrypter/hider, and managed to crack the (rather weak) encryption it uses.

So if any of you have any old disks you've forgotten the password to, here's my tool: https://github.com/ymgve/laurin-decrypt (Sorry for the low quality code)
2016-03-31 18:05
Count Zero

Registered: Jan 2003
Posts: 1809
Release on CSDb or didnt happen! :)
2016-03-31 22:40
lA-sTYLe

Registered: Sep 2003
Posts: 63
confirmed working ;-)
2016-04-01 19:27
AlexC

Registered: Jan 2008
Posts: 293
Very interesting. Where I can find original tool?
2016-04-01 19:31
Ymgve

Registered: May 2002
Posts: 84
Laurin is the one I studied, at least
2016-04-02 14:20
hedning

Registered: Mar 2009
Posts: 4550
Laurin-decrypt
2016-04-04 04:22
Style

Registered: Jun 2004
Posts: 498
Any details on the encryption method?

I always like to giggle at what people classified as "encryption" back in those days. I "cracked" a tacops anti-cheat proggy once that was basically using EOR "encryption". So much work went into it, but the stream could be broken just by staring at the bytes long enough.
2016-04-04 13:22
Ymgve

Registered: May 2002
Posts: 84
It takes an 8 character password, which it compresses down into 4-byte key, which is then "obfuscated" (but also restricts the keyspace) by using the BASIC ROM as a look-up-table. The final 4-byte key is then used for a function that works on individual bytes by doing add/xor/add/xor with the respective bytes of the key.

Encryption is done by RLE encoding the directory track and then encoding it. It's then written back to the directory track, with a fake track 18.0/18.1 placed instead.

You'll note that I only talked about the directory - Laurin doesn't even look at the actual file data, it only touches the directory track. So even if my program failed you would be able to recover the files on disk with any standard recovery tool.

Also, if any of you want to scan your collection for Laurin disks or something, it checks if byte 3 of sector 18.0 is 0x69 to verify that a disk is actually encrypted.
2016-04-04 13:33
iAN CooG

Registered: May 2002
Posts: 3128
Some probably had hundreds of these disks, and have reused them because they appear as empty formatted "testdisk". Very clever way to loose your precious data :D
RefreshSubscribe to this thread:

You need to be logged in to post in the forum.

Search the forum:
Search   for   in  
All times are CET.
Search CSDb
Advanced
Users Online
Flex/Artline Designs
Havoc937
t0m3000/ibex-crew
Jasmin68k
Guests online: 338
Top Demos
1 Next Level  (9.8)
2 Mojo  (9.7)
3 Coma Light 13  (9.7)
4 Edge of Disgrace  (9.6)
5 No Bounds  (9.6)
6 Comaland 100%  (9.6)
7 Uncensored  (9.6)
8 The Ghost  (9.6)
9 Wonderland XIV  (9.6)
10 Bromance  (9.6)
Top onefile Demos
1 Party Elk 2  (9.7)
2 Cubic Dream  (9.6)
3 Copper Booze  (9.5)
4 Rainbow Connection  (9.5)
5 TRSAC, Gabber & Pebe..  (9.5)
6 Onscreen 5k  (9.5)
7 Dawnfall V1.1  (9.5)
8 Quadrants  (9.5)
9 Daah, Those Acid Pil..  (9.5)
10 Birth of a Flower  (9.5)
Top Groups
1 Booze Design  (9.3)
2 Nostalgia  (9.3)
3 Oxyron  (9.3)
4 Censor Design  (9.3)
5 Crest  (9.3)
Top Swappers
1 Derbyshire Ram  (10)
2 Jerry  (9.8)
3 Violator  (9.8)
4 Acidchild  (9.7)
5 Starlight  (9.6)

Home - Disclaimer
Copyright © No Name 2001-2024
Page generated in: 0.187 sec.