Is it able to read NVPWD register with application code only in user mode?

cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Is it able to read NVPWD register with application code only in user mode?

Jump to solution
812 Views
Feiyang_Sun
Contributor II

Right now I'm using MPC56xx(SPC560P40) for a project that requires a password on OCDs which in my case is the JTAG interface. Also it requires the password "NOT READABLE OR WRITEABLE" with user codes.

Except hash the password(which I don't think make any difference since the hash operation can't be occurred after JTAG connection but before password inquire), how can I make sure that user code can't read or change the password?

0 Kudos
Reply
1 Solution
799 Views
petervlna
NXP TechSupport
NXP TechSupport

Hello,

I am not sure if I understood you correctly, but I will try to answer:

Except hash the password(which I don't think make any difference since the hash operation can't be occurred after JTAG connection but before password inquire), how can I make sure that user code can't read or change the password?

First of all SPC560P40 is device produced by STMicro and not NXP.

Second, this very old device apply only 1 protection to user code and that is censorship.

You can protect memory to be read out by setting JTAG/serial access password.

But if the application which is already in device has backdoors, it can remove/disable the censorship protection.

Have in mind that this is 20 years old design, where no security was required by customers...

In new devices, there is complex security scheme applied.

Best regards,

Peter

View solution in original post

0 Kudos
Reply
4 Replies
790 Views
petervlna
NXP TechSupport
NXP TechSupport

Hello,

Yes, that is the case. But if you leave serial communication unprotected, what benefit will bring you locked locked JTAG?

best regards,

Peter

0 Kudos
Reply
780 Views
Feiyang_Sun
Contributor II

Yeah I guess that's something we need to discuss with our customers...

Anyway, thank you for your support.

0 Kudos
Reply
800 Views
petervlna
NXP TechSupport
NXP TechSupport

Hello,

I am not sure if I understood you correctly, but I will try to answer:

Except hash the password(which I don't think make any difference since the hash operation can't be occurred after JTAG connection but before password inquire), how can I make sure that user code can't read or change the password?

First of all SPC560P40 is device produced by STMicro and not NXP.

Second, this very old device apply only 1 protection to user code and that is censorship.

You can protect memory to be read out by setting JTAG/serial access password.

But if the application which is already in device has backdoors, it can remove/disable the censorship protection.

Have in mind that this is 20 years old design, where no security was required by customers...

In new devices, there is complex security scheme applied.

Best regards,

Peter

0 Kudos
Reply
793 Views
Feiyang_Sun
Contributor II

Thanks for your reply Peter.

I get what you said.

So even if I brick the ECU, which is, I'm thinking of write NVSCI0 != NVSCI1, as long as I implement the software that leaves reflash function through serial interface like LIN interface, I can still reflash that code and rewrite NVSCI0 = NVSCI1 to enable JTAG interface, is that correct?

0 Kudos
Reply