How can i wipe user key (FUS/WS CKS) when all index positions are used?

[dd1]

For storing my crypto key I'm using the following function to store the key in the WB55 core 2 secure key storage:

uint8_t key_index = 1;
    SHCI_CmdStatus_t result;
    SHCI_C2_FUS_StoreUsrKey_Cmd_Param_t CKS_param;
    CKS_param.KeyType = KEYTYPE_SIMPLE;
    CKS_param.KeySize = KEYSIZE_32;
    memcpy(CKS_param.KeyData, key, KEYSIZE_32);
    result = SHCI_C2_FUS_StoreUsrKey(&CKS_param, &key_index);
    DPRINTF("Key stored at index: %d", key_index);

And than loading it into the aes crypto peripheral.

Al works fine until the index reaches the end positions(100 keys).

After that writing a new key will always fail.

I can't find a function to wipe the user key(s).

I there a way to achieve this?

How can i wipe or overwrite a user key?

I think I misunderstand the use of CKS...

[STea]

Hello @dd1 ,

Sorry for the delayed response. The maximum of keys that can be stored using FUS is 100 as stated in AN5185 (see section 5.1 Key types and structure) +one master clear key used to decrypt other keys if they are stored as encrypted. once stored you cannot neither remove nor update a key this is done to prevent key tampering as explained in this post.

BR