NRF9160-SICA-R7 datasheet(81/400 Pages) NORDIC

81 / 400 page

Peripherals

LCS field value

LCS_IS_VALID field value

Description

Secure

Invalid

Default reset value indicating that LCS has not been configured.

Secure

Valid

LCS set to secure mode, and LCS is valid. Registers HOST_IOT_KDR[0..3] can only be written once per reset cycle.

Any additional writes will be ignored.

Debug

Valid

LCS set to debug mode, and LCS is valid. Registers HOST_IOT_KDR[0..3] can be written multiple times.

Table 27: Lifecycle states

6.1.4 Cryptographic key selection

The CRYPTOCELL subsystem can be instructed to operate on different cryptographic keys.

Through register HOST_CRYPTOKEY_SEL on page 83, the following key types can be selected for

cryptographic operations:

• RTL key KPRTL

• Device root key KDR

• Session key

KPRTL and KDR are configured as part of the CRYPTOCELL initialization process, while session keys are

provided by the application through the software library API.

6.1.4.1 RTL key

The ARM TrustZone CryptoCell 310 contains one hard-coded RTL key referred to as KPRTL. This key is set to

the same value for all devices with the same part code in the hardware design and cannot be changed.

The KPRTL key can be requested for use in cryptographic operations by the CRYPTOCELL, without revealing

the key value itself. Access to use of KPRTL in cryptographic operations can be disabled until next reset by

writing to register HOST_IOT_KPRTL_LOCK on page 84. If a locked KPRTL key is requested for use, a zero

vector key will be routed to the AES engine instead.

6.1.4.2 Device root key

The device root key KDR is a 128-bit AES key programmed into the CRYPTOCELL subsystem using firmware.

It is retained in the AO power domain until the next reset.

Once configured, it is possible to perform cryptographic operations using the the CRYPTOCELL subsystem

where KDR is selected as key input without having access to the key value itself. The KDR key value must

be written to registers HOST_IOT_KDR[0..3]. These 4 registers are write-only if LCS is set to debug mode,

and write-once if LCS is set to secure mode. The KDR key value is successfully retained when the read-back

value of register HOST_IOT_KDR0 on page 84 changes to 1.

6.1.5 Direct memory access (DMA)

The CRYPTOCELL subsystem implements direct memory access (DMA) for accessing memory without CPU

intervention.

Any data stored in memory type(s) not accessible by the DMA engine must be copied to SRAM before it

can be processed by the CRYPTOCELL subsystem. Maximum DMA transaction size is limited to 216-1 bytes.

6.1.6 Standards

ARM TrustZone CryptoCell 310 (CRYPTOCELL) supports a number of cryptography standards.

4418_1315 v2.0

NRF9160-SICA-R7 Datasheet(PDF) 81 Page - Nordic Semiconductor

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