NRF9160-SICA-R7 datasheet(140/400 Pages) NORDIC

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Peripherals

be used, while the destination address determines where in the memory map the KMU pushes the key

value upon a request from the CPU.

Key slots can be configured to be pushed directly into write-only key registers in cryptographic

accelerators, like e.g. CryptoCell, without exposing the key value itself to the CPU. This enables the CPU to

use the key values stored inside the key slots for cryptographic operations without being exposed to the

key value.

Access to the KMU, and the key slots in the UICR, is only allowed from secure mode.

6.8.1 Functional view

From a functional view the UICR is divided into two different regions, one-time programmable (OTP)

memory and key storage.

Finite-state machine (FSM)

OTP

Key storage

0x1000

User information configuration register (UICR)

infopage

Access control

Functional view

User defined

Part specific instantiation

KEYSLOT.

CONFIG[0]

(…)

KEYSLOT.

CONFIG[n]

PERM

DEST

Permission legend:

Write-once per halfword limitation,

always readable

Write-once per halfword limitation,

always readable

Write-once per halfword limitation,

restricted usage and readability

based on key header configuration

UICR offset

Key values

STATE

PUSH

VALUE[0]

VALUE[1]

VALUE[2]

VALUE[3]

Regular UICR

Key headers

READ

WRITE

(…)

KEYSLOT.

KEY[n]

KEYSLOT.

KEY[0]

Figure 35: Memory map overview

OTP

One-time programmable (OTP) memory is typically used for holding values that are written once, and then

never to be changed again throughout the product lifetime. The OTP region of UICR is emulated by placing

a write-once per halfword limitation on registers defined here.

Key storage

The key storage region contains multiple key slots, where each slot consists of a key header and an

associated key value. The key value is limited to 128 bits. Any key size greater than 128 bits must be

divided and distributed over multiple key slot instances.

Key headers are allocated an address range of 0x400 in the UICR memory map, allowing a total of 128 keys

to be addressable inside the key storage region.

Note: The use of the key storage region in UICR should be limited to keys with a certain life span,

and not per-session derived keys where the CPU is involved in the key exchange.

6.8.2 Access control

Access control to the underlying UICR infopage in flash is enforced by a hardware finite-state machine

(FSM). The FSM can allow or block transactions, depending both on the security of the transaction (secure

or non-secure) and on the type of register being written and/or read.

4418_1315 v2.0

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