Thanks for the offer but I managed to compile it. So the encryption you mentioned refers to the keys used to encode the firmware, like the old dvd css key nonsense.
For anyone else who wants to compile CHDK for this camera here's a quick rundown:
Get CHDK-Shell. It has a simple gui and includes the entire tool chain to compile CHDK.http://chdk.wikia.com/wiki/CHDK-Shell
Get the 'full' version and extract it. Then get the 'update' version and extract it on top.
Then dig up v343a attached to a forum post and replace the main exe. This last patch fixes the ability for the program to download the latest trunk source code.
So then start the CHDK-Shell, click the checkmark "allow internet" and it will download the latest trunk from svn. It will appear to hang but just wait it out. When that's done checkmark the SX210IS 100C build.
It's ready to compile.
If you want to build a version you can run with the firmware update method you have to obtain the encoding keys specific to your camera model and add them to a build file.
Hit the 'Compile Options' button and select 'OPT_FI2'
You have to copy this sample file and rename it to fi2.inc
Open it in a text editor it should be fairly obvious where the keys go.
(Of course later on, trunk2642 will be some other version number so don't use my paths literally.)
The keys are not readily available and you have to go on a hunt.
Find the 8k firmware dump for the SX210IS 1.00C:http://chdk.setepontos.com/index.php?topic=5045.msg81866#msg81866
Identify the offsets for the bytes you need based on camera model:http://chdk.wikia.com/wiki/For_Developers/fi2offsets
Open the firmware bin file in any standard hex editor. Go to the offsets indicated and copy the 16 bytes in hex format into the fi2.inc file. I used lowercase, probably makes no difference. Remember to save the file.
Now just hit the compile button in CHDK-Shell
When the "100C" beside the SX210 checkmark turns green the compile is done.
Otherwise if the compile fails you will probably get a text document opening on your screen with error messages.
The CHDK files you need to extract to the root of your sd card are all packed nicely into a zip file:
That's it. I hope that will save the next guy some time.
Now that I can run the latest chdk versions I hope to test out more features and feed that info back so we can get this build mainstream.