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Thread: Help decoding embedded dashcam database

  1. #1
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    Default Help decoding embedded dashcam database

    Wasn't real sure where to place this request. I'm looking for a bit of general help in decoding an embedded database in a car dashcam - the database is used to alert the driver of approaching red light / speed cameras.

    Bit of context here: there's two versions of this dashcam on the market:
    • One that has it's database updated less frequently, and appears to use a more simple (XOR?) hash to scramble the database.

    • Another model which uses the same hardware platform, firmware etc developed by the same manufacturer, but the database is updated more frequently, and it appears as if they use a different method to scramble the database.


    The devices are primarily aimed at the USA market, and I'd like to see if the database can be more comprehensively customised for my region - hence the motivation to decode the database. Here's what I've been able to do so far:

    Taking the firmware update image of the more 'simple' version device, extracting what I know to be the database and assuming the tail end of the data should decode to either 00 or FF, the result looks a lot like what it should as far as NMEA / GPS co-ordinates & a few flags following - it might not be what it should decode down to exactly, but it looks like a good start:



    But then doing the same with the other device - the one I'd like to work on - is very different. After trying a few likely XOR hashes, the data distribution is still very uniform and doesn't look at all like what it should. The 'scrambled' data is stored exactly as is on the device's flash memory, suggesting that the MCU decodes this data 'on the fly' as it needs to use or refer to it. So the encoding method probably isn't going to be too complex, I'd be guessing?


    I can't extract the MCU CortexM0 code (either the program locks are set, or this device doesn't use standard JTAG or SWD interface?) to get any clues on how it might be decoding on the fly, either, unfortunately. The firmware update image for the MCU code appears to be similarly scrambled - I can see evidence of a repeating pattern typical of a vector table, but it's clearly been scrambled too.

    Any pointers on how to progress would be appreciated



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    Just curious ~ you can't install the Waze app on the vehicle infotainment system? It would be easier =)

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    Sure could - and have it on the smart phone already - but I like a challenge and to learn new things

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    Fair answer =) What is the dashcam/vehicle?....

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