Ok, it’s ugly and illegal, i know. The information here is for educational purposes only.

Sometimes i’m asked to “cure” one or another product, protected by registration or network license manager, like FlexLM. And you know, a lot of keygens for these product found in the Internet, do not work. The usual error is “Internal Error #{1..6} – Please be sure the app is running and on the license screen!”. What’s wrong, why the keygens from the glorious crack groups do not work any more?

Search on the Internet revealed almost nothing: from “the kyegen does not work” to “it works perfectly”, some says one must use genuine windows the keygen to work (wow…).

Let’s start a little investigation.

Some keygens are packed with some kind of packer, like UPX. I’m too lazy to extract them.
So i’ve found an unpacked version of keygen for AutoCAD 2008, created an evaluation installation of AutoCAD 2008 from Autodesk Revit Architecture 2008 (i have a license for it to run on the network, by the way) and started my explorations.

A usual PE executable consists of some sections: header, data, imported functions, static variables and text resourses. Text resourses are usually located near the end of the file, and it is the very first place to look for an information.
The very first string’s i have noticed, at the very beginning of text resourses were “acad.exe” and “~de81d5.tmp“. But wait, when running AutoCAD, i have 4 files with constant names in “%TEMP%/AdskCleanup.0001.dir.0000”. Their names are “PfdRun.pfd“, “~de0acb.tmp“, “~df294b.tmp” and “~efe2.tmp“. Only two of them has names with 7 symbols (like in keygen’s “~de81d5.tmp”). The *.tmp files seems like PE executables.
A quick edit in the keygen to match the actual names and …

The mysterious error is gone, you can paste a request code in the keygen.


Let’s summarize:

  • every product line Autodesk ships uses unique set of registration keys. This also means that AutoCAD 2008 sold as separate product will have different encryption keys that the AutoCAD2008, sold as “Revit Architecture suite 2008”;
  • the keygen searches for predefined file in “%TEMP%/AdskCleanup.0001.dir.0000”, extracts encryptions keys (?) and generates authentification code, depending on your request;
  • if the keygen does not find a predefined file in the predefined place, a famous “Internal Error #…” will be generated;
  • as keygen works with predefined location of encryption keys, it is not capable of generating authentification code for different products

So, what’s to do if You got the famous “Internal Error #..”?
Buy the product. Or search for another keygen.