Decrypting TMC Messages
 

I am in Australia and am trying to access the new RDS-TMC service which BMW is not supporting at the moment as is unlikley to support for earlier build cars.

I have MK4 Navigation with a BM54 Tuner (new) which supports TMC and dynamic routing.

The RDS-TMC Service here is techically aligned with the UK i-TMC service however you have to pay for it, therefore it uses encryption and conditional access using Alert-C coding.

Does anybody know if I it is possible to update the nav os so it can decrypt incoming tmc messages?

Would I be able to add the appropriate access codes (that I would get from the TMC provider) to the os software using something like Navtweak or any other programs.

Or does anybody know someone that can help with this or point me to a website or forum that might cover this area?

Not that simple.

To make TMC work you need:

1. A map disc with the TMC database on it. The database references the broadcasted TMC location IDs to real lat/long positions on the map. Who holds the master TMC location database for Australia? Probably the TMC-provider. And they won't give it to you for free...
Then you have the problem of compiling a new map CD with the new TMC database... I don't know how easy that is. Maybe just add the new TMC database file? In what format? Maybe integrate with the map data somewhere...


2. You also need to change the nav software to decrypt the TMC message. To do this you need to get access to the nav source code, and know the encryption/decryption used on the TMC. The nav is written in OS9000, which is now very very old. You would need to reverse compile the OS9000 source code, understand it, rewrite it, and recompile. You thus need to be an expert in OS9000. And you also need a good source of Mk4 navs as the chances of corrupting the flash and killing the nav are extremely high. Or else you need the ability to reflash the nav manually.

So whilst nothing in this world is impossible, some things are simply very, very hard...

PS: understanding the TMC protocol is also a bit of a challenge - I have added some TMC decoding in NavCoder, but can only decode to Location IDs. The cross-reference from Location ID to Lat/Long is held on the map, and thus is not visible to NavCoder.

Get a hold of the TMC standards doc to understand the TMC protocol.
Heavy reading, but fascinating...

in short, sounds like a no ! :)

Thanks for your reply Jochen.

The latest Australian nav discs have TMC location tables.

The system being used here is the same as in Europe but with Encryption and Conditional Access, are there any countries in Europe that have an RDS-TMC service with Encryption and Conditional Access?