K82 flash locking

[chriswestervelt]

I’m full steam ahead using the K82 part for an encryption dongle.  I could use some help figuring something out though.  I need to be able to load keys and certificates on to the part and store them in NAND flash.  I also need to lock the NAND after programming so no one can pull code (or keys etc.) from the SWD.  Will that be a conflict and keep me from being to commit data to the NAND from inside the part with it locked?

[Jonathan_Iglesias]

Hi Chris Westervelt,

To set the security you will have to modify the address 0x0_040C this address is a byte long.

I think the  important thing here for you is the 

•  KEYEN.- this is the Key enable, you can set a backdoor key to acces . this key will temporary unsecure the MCU so you can modifiy whatever you need and when you reset the MCU will be secured.
• SEC.- When this is Enabled the MCU is going to be secured

Please check the http://www.nxp.com/assets/documents/data/en/reference-manuals/K82P121M150SF5RM.pdf  reference manual in the chapter 10.

Please let me know if you have more questions.

(Please try to set the mass erase to enable otherwise, if for some reason you forgot your backdoor key you can erase the MCU and use it again)

Have a great day

Best Regards

Jonathan

[chriswestervelt]

From the documentation it appears that the SEC field will lock access from the SWD interface and that I can still have my software internally write nonvolatile data to NAND as needed.  Is that correct?