BT 2.1 - SSP initiated by a BTM module

This article is designed to illustrate the process of Simple Secure Pairing (SSP) when initiated from a BTM module. Introduced in Bluetooth v2.1, SSP creates a bond in a very different way than the legacy PIN pairing many users are familiar with. This is demonstrated both for security level 2 (default) and security level 3.

Security Level = 2

Assumptions:

peer device is BT2.1 (supporting secure simple pairing)

security level of BTM device is

security level of peer device is

the pairing initiating device is aware of the peer device's Bluetooth Device Address

Note:  Connections in Bluetooth v2.1 are always encrypted.

Figure 1:  BTM vs BTM

Figure 2:  BTM vs PC

Security Level = 3

Assumptions:

peer device is BT2.1 (supporting secure simple pairing)

at least one device with security level = 3 (MITM protection / authentication enabled)

the pairing initiating device is aware of the peer device's Bluetooth Device Address

Remarks:

Connections with BT2.1 are always encrypted

"MITM" = Man-In-The-Middle. "MITM protection" means "protection against a MITM attack".

MITM protection is equivalent with authentication

Figure 3:  BTM vs BTM, security level 3

Figure 4: BTM vs PC, security level 3