Detailed Description

Introduction

Figure 1. BLE Stack: SMP

The SMP subsystem implements the security manager protocol. It contains two independent subsystems:

• The initiator (SMPI). SMPI implements the initiator features of the security manager protocol and has support for multiple simultaneous connections.
• The responder (SMPR). SMPR implements the responder features of the security manager protocol and has support for only one connection.

SMP also implements:

• The cryptographic toolbox, which uses AES. The interface to AES is asynchronous and abstracted through WSF.
• Functions to support data signing.

An SMP layer below SMPI and SMPR implements routing of received SMP protocol messages to either SMPI or SMPR.

When connected in the central role, the following configurations are possible:

• SMP Secure Connections Initiator
• SMP Legacy Initiator

When connected in the peripheral role, the following configurations are possible:

• SMP Secure Connections Responder
• SMP Legacy Responder

For full API see Security Manager API.

SMP Secure Connections Responder

Introduction

This is the SMP Responder role for a connected device in the peripheral role when the Secure Connections feature is enabled. A peripheral device may initiate pairing with an SMP Slave Security Request or by waiting for the central device to send an SMP Pairing Request. A Secure Connections enabled peripheral device prefers to use the previously mentioned feature to pair, but may fall back to Legacy behavior if configured to do so.

SMP Secure Connections Responder Behavior

Here is the state machine for SMP Secure Connections Responder Pairing Behavior

SMP Legacy Responder

Introduction

This is the SMP Responder role for a connected device in the peripheral role when the Legacy SMP configuration is used. A peripheral device may initiate pairing with an SMP Slave Seucrity Request or by waiting for the central device to send a SMP Pairing Request.

SMP Legacy Responder Behavior

Here is the state machine for SMP Legacy Responder Pairing Behavior.

SMP Secure Connections Initiator

Introduction

This is the SMP Initiator role for a connected device in the central role when the Secure Connection feature is enabled. A central device may initiate pairing by sending an SMP Pairing Request or by waiting for the peripheral device to send an SMP Slave Security Request. A Secure Connection enabled central device prefers to use the previously mentioned feature to pair, but may fall back to Legacy behavior if configued to do so.

SMP Secure Connections Initiator Behavior

Here is the state machine for SMP Secure Connections Initiator Behavior

SMP Legacy Initiator

Introduction

This is the SMP Initiator role for a connected device in the central role when the Legacy SMP configuration is used. A central device may initiate pairing with an SMP Pairing Request or by waiting for the peripheral device to send an SMP Slave Security Request.

SMP Legacy Initiator Behavior

Here is the state machine for SMP Legacy Initiator Pairing Behavior.