[vtl]

I don't have any confidence in any of the downgrade functions of CGDI either, seems to be good for reading ISNs out of MS80/81 though, which is the primary reason why I bought it. That's good to know about the unlock key function. 

Is it possible to transfer keys from one CAS to another by simply copying the key data slots across? Looks like the dump you edited for me only changed the ISN data locations and none of the key data. 

Looks like I may need to invest in a Hexprog next. Bit steep purchase just to change ISN in a CAS but might be worth it in the long run.

[RocketSurgeon]

What are you wanting to do with key data? Are you trying to make one key work on multiple vehicles or something? If you just want to reuse keys, there are key unlock tools that flash virgin firmware starting at $130. 

The hexprog editor only works for mileage, VIN, ISN, etc. It works very well, but it only has a handful of features. Key unlock is also pretty sweet, and reading CAS4+ without removing components. Admittedly the price is a little steep, and I have had some difficulties using it for KOMBI EEPROM.

There are a couple of programs designed to edit CAS dump ISN and key data. I don't have any personal experience with them, but they may do what you want. There's one on eBay for $90, or a member of this forum is working on a VERY cool program for this. I'm not quite sure how you decrypt though, since you either need hardware that can read a key, or you need to know the ISN.

[vtl]

Basically, im trying to figure out a way to make this CGDI workable for even the latest software version, even if it might be a bit of a roundabout way to do it.

My main usage scenario: Water damaged MSD80/81, MOSFET failures on MSD80, or people who simply want to upgrade to MSD81. Get these donor DMEs to work with the original CAS and keys. 

Currently, I can downgrade a CAS using R270 to version 9226238 which is fully compatible with CGDI (this I have a dump of EEPROM and FLASH). I can read the ISN out of the DME and write the CAS without any hassle. Can also program new keys. I successfully added a new key without knowing the ISN or having an existing key to it (all keys lost situation). 

My thought is that I can downgrade a CAS in order for CGDI to work with it, write the ISN into it, but then the original keys would no longer work, as the matching 9226238 EEPROM data has a different set of keys programmed into it. If I could then add the original keys to the CAS via the original dump, that would be the final piece of the puzzle. Final result would be the original keys start the car with the original CAS and new DME. 

The main thing is that the original keys are used and are not cut open. I am not a fan of the idea of cutting open the keys, seems like it would be quite time consuming splitting open and regluing the case, and would never be as good as the original. 

Yes this is a bit convoluted but just thinking out aloud here. 

I've seen a tool called CAS3+ editor on youtube which was able to decrypt a CAS, basically exactly what I want but couldnt see a place to buy it, and not sure if it would work. It would be useful even with CGDI, since it is still able to read the ISN on 9395657, just cant write it.

[vtl]

Big thanks to RocketSurgeon for providing me with an edited dump and worked great!

I eventually managed to figure out a way to get the new ISN written into CAS units with my current setup, took a bit of effort. I ended up completing a working bench setup so I could experiment with different things.

The ISN cannot be written into the CAS by CGDI, unless its an older CAS version. I believe it needs to be lower than v45. The ISN cannot simply be copied across from one unit to another because it is 'encrypted'. From trial and error, looks like this is based on the key data, but the key data itself doesn't change when you change the ISN. So for CAS3+ ISTAP, the 3 lines of 16 byte ISN data is generated from the actual ISN, with the key data as the input. 

Using the tool CAS3+ editor as a reference I defined a new XDF file in TunerPro for CAS3 units. This allows easy manipulation of the CAS data.