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Author Topic: anti-tamper circuit for Arduino Mega  (Read 3210 times)
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Thanks guys, lots of good ideas.

The device in question is a gps data logger designed for long-distance cycling. The requirements are the organisers, not mine. I think it's overkill, but the idea is that the data integrity needs to be guaranteed whilst the device is on and logging, and the device integrity needs to be guaranteed even when the device is powered down. The main power for the device is external, I could add an extra internal button cell just for the anti-tamper circuit, but then I'd have to add circuitry to charge it.

The data being written to the SD card is encoded, the idea is that every time the device is powered up it will check if it's been tampered with, and write the results of that check (in an encrypted format) to the SD card. So long as no-one works out how to write encoded data to the card themselves then the data should be secure.

The use of low power sleep mode looks good - I wasn't aware the arduino had this option, I'll do some research on this. Thanks
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Use the paper seals and write firmware to force creation of sequentially numbered files.  Each reboot creates the next file, never a repeat.  While everyone is waiting to start, the data will accumulate to file # x.  A few minutes before the race starts every one presses the reset button.  File  # x+1 is created.   After the end of the race the box is reset again and file x+2 is created and logs a little data.  The timing, presence of the file, and the continuity of data verifies the validity.

If the race goes for more than one day, the thing is shut down with or without opening the box and process starts again in the morning with a new sequential file.  If the battery is changed or other accident, it will start over when power is applied.

A secure web based application would accept upload of the data, provide as much scrutiny to the recorded data as desired, format the data and allow public access to view it.
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