JP1 Remotes

sfhub · Joined: 12 Oct 2003 Posts: 287

It seems EFCs are some sort of transcoding of OBCs achieved through
reordering bits, flipping some bits, and some operations to fit within 8bits.

I'm trying to understand what was the rationale behind creating EFCs
vs just using OBCs? There seems to be a 1-to-1 mapping but OBCs
are more logically laid out.

Are the OBCs proprietary and EFCs are some sort of UEI obfuscation or
something else entirely?

jon_armstrong · Posted: Tue Apr 13, 2004 6:00 pm Post subject:

I think it was an attempt to encrypt the OBC and IIRC decrypted by John Fine long before the JP1 effort started. Also, since some OBC's < 8 bits and the EFC's are always 8-bits, then the spare bits do useful things like call alternate devices or trigger different behavior needed by certain devices.
_________________
-Jon

The Robman · Posted: Tue Apr 13, 2004 6:56 pm Post subject:

They were definitely created as an encyption device. UEI is paranoid in a major way about protecting their IR database, so they don't want people understanding what the codes are all about (yeah, that really stopped us, eh?). After all, why would they go to the trouble of adding special code to their remotes so that if you change setup codes on a specific device button too many times in a row, they keypad becomes scrambled? They obviously figure that someone is trying to pirate their codes.

Jon is correct, John Fine did decode the OBC/EFC thing long before JP1 started. Apparently, some of the big wigs at UEI were quite chocked to learn that we knew how to decode EFCs
_________________
Rob
www.hifi-remote.com
Please don't PM me with remote questions, post them in the forums so all the experts can help!

johnsfine · Posted: Wed Apr 14, 2004 6:49 am Post subject:

John Wasser also figured out how to decode EFCs (with just one minor detail wrong, IIRC). And he did it with far less information available than I had (I knew the OBCs for a couple devices, but he had to guess at all OBCs) and he posted it on the web (which I hadn't done). When I saw he had done that, I emailed the minor correction to him. But if you're handing out credit for cracking that code, he "published" first.
Rob has a copy of John Wasser's updated (since he first published that stuff) but still obsolete now web site at
http://www.hifi-remote.com/wasser/index.shtml

sfhub · Joined: 12 Oct 2003 Posts: 287

Thanks guys for making it clear why UEI made the clear unclear. Smile