Is it possible to check if a KMU slot is used ?

[NelsonGoncalves]

Hello,

 I am using NCS v1.5.0 and would like to check is a KMU slot is being used or not. I erased the whole SoC and tried reading the directly the registers, in secure mode, as follows:

uint8_t hasKey = 0;
uint8_t i = 0;

for (i = 0; i < 4; i++)
{
    uint32_t value = NRF_UICR_S->KEYSLOT.KEY[2].VALUE[i];

    if (0xFFFFFFFF != value)
    {
        hasKey = 1;
        break;
    }
}

but the value is always 0xdeaddead. The same value is read when a key was present in the KMU slot.

I searched the NCS libraries and it seems it only supports writing a key into a KMU slot.

Is it possible to check if a KMU slot is in use ? 

Best regards, 

 Nelson

[Hakon]

Hello,

but the value is always 0xdeaddead.

From the KMU documentation;

"Step 2 will be blocked and word 0xDEADDEAD will be returned on AHB if any of the following violations are detected:

• No key slot selected
• Key slot not configured as readable
• Key slot is revoked
• AHB read to KEYSLOT.KEY[ID-1].VALUE[0-3] registers not belonging to selected key slot"

 

 

Is it possible to check if a KMU slot is in use ? 

 I'm not aware of any ways to check this, but you can look at this and this and see if there are any registers you can use for that.