PM0237 datasheet(63/88 Pages) STMICROELECTRONICS

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PM0237

Design an application using BlueNRG, BlueNRG-MS ACI APIs

3.5

Security (pairing and bonding)

This section describes the main functions to be used in order to establish a pairing between

two devices (authenticate the devices identity, encrypt the link and distribute the keys to be

used on coming next reconnections).

When using the security features, some low level parameters (root keys) must be set,

before raising any other ACI commands:

•

DIV root key used to derive CSRK

•

Encryption root (ER) key used to derive LTK and CSRK

•

Identity root (IR) key used to derive IRK and CSRK

The external microcontroller (MCU) has the responsibilities to provide these parameters as

follows:

It has to randomly generate the three root key values (if not already generated) and

store them in a non-volatile-memory. The three root keys have to be generated only

one time, in order to univocally establish the specific BlueNRG, BlueNRG-MS device

security settings.

Each time the MCU starts, it has to read the root keys from the non-volatile-memory

and set them during the initialization phase of the BlueNRG, BlueNRG-MS device.

Following is a simple pseudo code showing how to set the read randomly generated

security root keys on BlueNRG, BlueNRG-MS devices:

uint8_t DIV[2];

uint8_t ER[16];

uint8_t IR[16];

/* Reset BlueNRG, BlueNRG-MS device */

BlueNRG_RST();

/* Microcontroller specific implementation:

1) MCU has to

randomly generate DIV, ER and IR and store them in

a non volatile memory.

2) When MCU starts it has to read DIV, ER and IR values from the

non volatile memory.

………

/* Configure read root key DIV on BlueNRG, BlueNRG-MS device

ret = aci_hal_write_config_data(CONFIG_DATA_DIV_OFFSET,

CONFIG_DATA_DIV_LEN,(uint8_t *) DIV);

/* Configure read root key ER on BlueNRG, BlueNRG-MS device */

ret = aci_hal_write_config_data(CONFIG_DATA_ER_OFFSET,

CONFIG_DATA_ER_LEN,(uint8_t *) ER);

/* Configure read root key IR on BlueNRG, BlueNRG-MS device */

PM0237 Datasheet(PDF) 63 Page - STMicroelectronics

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