Preventing reprogramming an nrf52832

RE: Preventing reprogramming an nrf52832

karthikeyan — Fri, 23 Feb 2018 04:11:22 GMT

thanks edvin

RE: Preventing reprogramming an nrf52832

Edvin — Thu, 22 Feb 2018 15:26:06 GMT

Well. If the SWDIO and SWCLK are shorted to GND, there is no way to program it. The only way to program it then would be through a bootloader, but this would have to be programmed in before the chip is soldered to the pcb, or at least before the SWDIO and SWCLK are grounded.

RE: Preventing reprogramming an nrf52832

Matt — Wed, 21 Feb 2018 14:04:58 GMT

If folks are desperate to reprogram your chip they'll always find a "way". You have to think system protection then i.e. how would the "other" side verify the identity of your chip.

RE: Preventing reprogramming an nrf52832

karthikeyan — Wed, 21 Feb 2018 06:31:50 GMT

hi edwin,

similar question to me. but i am programming the chip after soldering in my custom pcb. so after that how can i give protection. i need suggestion from hardware not in software.

RE: Preventing reprogramming an nrf52832

Matt — Mon, 19 Feb 2018 13:43:27 GMT

The Decepticons are working on it... any "Transformer 6" fans here? :)

RE: Preventing reprogramming an nrf52832

Edvin — Mon, 19 Feb 2018 13:18:12 GMT

Hello,

There is no way in software to prevent an erase and reprogramming of the nRF if they have physical access to the programming pins of the nRF, but as you say, there is readback protection, to prevent them from reading the .hex file programmed to the chip.

What you could do, is to pre-program the chip, before soldering it on to the PCB. Then, on the PCB, you can ground the SWDIO and SWDCLK. This will make it impossible to program the chip unless you desolder the chip. In my opinion, if someone is able to desolder the chip, they might as well change the entire PCB with their own chip and firmware.

BR,

Edvin

RE: Preventing reprogramming an nrf52832

Matt — Sun, 18 Feb 2018 02:08:15 GMT

Do you have control on the other end (eg. the GAP central / GATT client)? If you do then at least you can add some identify verification on the other end to identify the malicious app.

RE: Preventing reprogramming an nrf52832

SRA — Sat, 17 Feb 2018 19:36:51 GMT

Yea, and it doesn’t actually work that well. Plus the serial bootloader stays on and can’t be turned off.

RE: Preventing reprogramming an nrf52832

Turbo J — Sat, 17 Feb 2018 16:33:00 GMT

NXP LPC176x has a "magic" value in flash that can disable both ROM bootloader and JTAG/SWD. The chip is locked for good unless there is a way to erase/flash in the customers firmware.

RE: Preventing reprogramming an nrf52832

SRA — Sat, 17 Feb 2018 15:22:50 GMT

I can’t think of any. Almost all cortex M parts that “disable JTAG/SW” do so for debug read/write commands but you could still recover/reset the chip with an erase. I have yet to see a Cortex M part with a lifecycle implementation.

Are you just being overly concerned about your physical device that could surely be cloned?

if I was tasked to do this, I guess I would program the firmware off the board, then solder the chip on to a board with internally shorted SW pins. That way the only access to program would DFU or desolder.