USER MANUAL
PTM 216B – BLUETOOTH
®
PUSHBUTTON TRANSMITTER MODULE
© 2022 EnOcean | www.enocean.com
F-710-017, V1.0
PTM 216B User Manual | v1.0 | February 2022 | Page 76/86
C.
Authentication of PTM 216B data telegrams
PTM 216B provides the option to authenticate its data telegrams as described in chapter
4.6.3. The authentication mechanism used by PTM 216B is standardized as RFC3610. The
full RFC3610 specification could be found here at the time of writing and should be used as
primary source of information:
https://www.ietf.org/rfc/rfc3610.txt
The following description aims to summarize the security processing steps for users not
deeply familiar with cryptography in general or RFC3610 in particular.
C.1
Algorithm input parameters
The purpose of the security processing in PTM 216B is to calculate a unique signature that
can be used to verify authenticity (telegram has not been modified) and originality (tele-
gram comes from the assumed sender) of a telegram.
To
do
so,
two
types
of
algorithm
parameters
are
required:
Constant
algorithm
input
parameters
These parameters identify high level algorithm and telegram properties and are the
same
for
any
PTM
216B
telegram
Variable
algorithm
input
parameters
These parameters identify telegram-specific parameters and therefore depend on
the specifics of the transmitted telegram
C.1.1
Constant input parameters
The RFC3610 implementation in PTM 216B requires two constant input parameters:
Length
field
size
This is the size (in byte) of the field used to encode the length of the input data
(which
is
the
payload
to
be
authenticated).
The maximum size of PTM 216B payload to be authenticated is 13 byte; therefore
one byte would be easily sufficient to encode the payload size. The minimum value
permitted by the standard is however 2 bytes which is therefore chosen.
Signature
size
This is the desired size of the generated signature which is 4 byte for PTM 216B
Table 11 below summarizes these constant algorithm parameters.
Parameter
Comment / Description
Example
Length
Field Size
Size (in bytes) of the field used to
encode the input length
2
(always, minimum permissible size)
Signature
Size
Desired size (in byte) of the signa-
ture generated by the algorithm
4
(always)
Table 11 – Constant algorithm input parameters
