Thread: [CompeGPS TwoNav] HELP decoding .rmap file format

Hi everyone,
I've some raster maps in *.rmap format that i can use with Twonav on my Android device, however i want to extract all the tiles to create jnx files for my Garmin. These maps are locked in some way (can't move on other devices, a code would be asked).

I've made a simple rmap file with MOBAC and i've noticed that in this file images are clearly recognizable by their signature (eg. FF D8 FF for jpeg). This file is also readable on all devices.

However maps bought and downloaded with Twonav have data obfuscated in some way. The first part of the file is a list of binary offset to actual data, that have to be decoded (i suppose) to become an image. I've got some addresses from where maps are downloaded, and i can say that the files are always the same, regardless the device used to download. So the key to decode should be device independent and stored into the app.

At this point i've tried to decompile the app with dex2jar but i've found nothing (i could be wrong! first time i try...). Sadly most of the app is written in native code, and reverse engineering that is currently out of my reach.

This is an example of a locked .rmap file:
[Only registered and activated users can see links. ]
(This particular file is supposed to be a free demo, but it's actually locked so i'm not able to open it)

So if someone have an idea on how to extract images contained into the rmap file, or can help me in some way, i'll appreciate a lot!