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 35 of 66
AT+BMITM controls the man in the middle (MITM) protection of the device during LE
Security.
Value Description
0
Man in the middle protection disabled (default)
1
Man in the middle protection enabled
LE Security defines the following association models based on the Input/Output (I/O)
capabilities of the two devices:
•
Just Works:
This method is used when at least one of the devices does not have display capability of six
digits and also is not capable of entering six decimal digits using a keyboard or any other means
(no I/O).
This method does not provide MITM protection (see 5.4 Connection Example Terminal I/O
“Just Works”).
•
Passkey Entry:
This method may be used between a device with a display and a device with numeric keypad
entry (such as a keyboard), or two devices with numeric keypad entry (see 5.5 Connection
Example Terminal I/O “Passkey Entry”).
In the first case, the display is used to show a six digit numeric code to the user, who then enters
the code on the keypad.
In the second case, the user of each device enters the same six digit numeric code.
Both cases provide MITM protection.
Possible combinations of I/O capabilities and the possibility of MITM protection are listed in
the table below. For each case of the “MITM protection” an example of the serial messages
between the S42/Central and the DTE are listed.
In case the user choose a scenario where MITM protection is not allowed but one of the
communication devices is configured to MITM protection, the pairing is refused.
•
Numeric Comparison:
This method may be used between two devices with a display and keys that allow the user to
accept or reject a connection.
If the “Display Yes/No” or “Display and keyboard” capability is supported by both devices the
displays show a 6 digit numerical code. The user is then requested to compare the codes of both
displays. If the codes on both displays are equal the user can accept the connection by pressing
the “yes” input of both devices. In case the user presses the “no” input on at least one of the
devices the pairing becomes rejected.
This method provides MITM protection.
