Contents of the unique device ID registers LOT_NUM

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I'm using STM32L031E6Y6 for a high volume low cost product and I'm hoping to arrange it so that even if my firmware binary were to be stolen, it could only be used to produce a limited number of counterfeit products.

I can cryptographically fix the firmware so that it will only run if the LOT_NUM part of the device ID registers is within a certain range but how many unique devices might share the same lot number ?

Also, is it probable that all the devices on a reel share the same lot number and is it possible to discover the lot number(s) before flashing the devices ?

STM32L0 series

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Piranha

Principal III

The one, who can pull the firmware from a protected MCU, definitely can also patch that firmware to bypass the ID test.

MMora.6Author

Associate II

You're correct of course but I'm more concerned about someone in my supply chain copying the firmware that I give them. I'm not expecting to make it impossible, just more difficult and I'm hoping to do it without spending a lot of money.

Piranha

Principal III

There are flashers that can be operated standalone without PC and can be locked to not allow the readout of stored files. Consider using such devices at manufacturing. For examle:

https://www.segger.com/products/flasher-in-circuit-programmer/

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