S42/Central Software User Guide
1VV0301318 Rev. 3
– 2018-08-31
Reproduction forbidden without written authorization from Telit Communications S.p.A.- All Rights Reserved.
Page 33 of 66
5.
Security
This chapter describes the security mechanisms of the S42/Central to control the
access to the local Bluetooth devices characteristics. The pairing process is triggered
automatically when an access to a characteristic is requested that requires security.
5.1.
Pairable and Bondable Mode
In general we distinguish between pairing and bond. Pairing is the active process to generate a
set of encryption keys. The paring can be done with or without user interaction depending of
the I/O capabilities. The pairing will result in a bond if the generated data is stored in the bonded
device list (AT+BNDLIST).
AT+BPAIRMODE controls if a pairing is performed or not.
Value
Description
0
No pairing (pairing request will be refused)
1
Pairing
AT+BNDS controls the storing of the pairing information as bond.
Value
Description
0
No storing (no bond)
1
Storing (entry in the bonded device list)
The bonded device list is affected by the following commands:
•
AT+BNDLIST
shows the devices stored in the bonded device list
•
AT+BNDSIZE
determines the size of the bonded device list and deletes the whole
list when modifying the size
•
AT+BNDDEL
deletes single entries or the whole list
•
AT&F1
deletes the bonded device list
If the bonded device list is full and another device is bonded, the least recently used device will
be overwritten by the new one. If bonds are not required please set AT+BNDS=0.
5.2.
LE Secure Connections
Bluetooth 4.2 supports a new security mechanism called “Secure Connections”.
LE Secure Connection introduces a new method to generate a shared secret (key) in a way that
ensures the data integrity and privacy of a connection even in cases where the pairing/bonding
procedure was completely tapped with a Bluetooth sniffer if that shared secret is used for
authentication and encryption.
Secure connection key generation is applicable for all authentication methods (e.g. just works
or passkey entry) while all authentication trigged I/O activity remain the same as for legacy LE
security but one new method (display yes/no) is introduced.
Bluetooth 4.2 mandates that LE Secure Connection key generation is used while
pairing/bonding if both devices of a given connection support this feature. If one device of a
