USER MANUAL
ESRPB / EDRPB - EASYFIT BLUETOOTH® SINGLE / DOUBLE ROCKER PAD
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F-710-017, V1.0
ESRPB / EDRPB User Manual | v1.3 | Jan 2018 | Page 59/68
B.1.2
Variable input parameters
The RFC3610 implementation in PTM 215B requires four variable input parameters:
Source address
The 6 byte source address used to identify the sender of an authenticated message.
The source address is required in little endian (least significant byte first) format.
Input data (Payload to be authenticated)
The authenticated payload contains source address, sequence counter, switch status
and optional data (if present). See chapter 4.8 for a description of the authenticated
payload.
Input length (Size of the payload to be authenticated)
The length of the payload to be authenticated depends on the amount of optional
data used in the telegram. This is configured via the Configuration register, see
chapter 6.7.6.
By default, no optional data is present and the length of the authenticated payload
is 9 byte.
Sequence counter
Each PTM 215B contains a sequence counter which is initialized to zero during pro-
duction and increased for each telegram that is sent.
The sequence counter is transmitted as part of the input data.
The receiver of PTM 215B telegrams keeps track of this counter and will accept only
telegrams with counter values higher than the highest previously used value. This
eliminates the possibility of reusing previously transmitted telegrams.
Note that the individual (identical) advertising telegrams used to encode the same
data telegram use the same sequence counter value.
Security key
Each PTM 215B is programmed with a random 16 byte security key during manufac-
turing. This key can be modified using the NFC interface, see chapter 6.7.3.
Parameter
Comment / Description
Example
Source
Address
Unique source address of the
PTM 215B module (little endian)
B819000015E2 (little endian represen-
tation of E215000019B8)
Input Data
Telegram data to be authenticated
0CFFDA03D00A000003
Input
Length
Length of input data (in bytes, en-
coded using 2 bytes)
0x0009
(if optional data size = 0, default)
0x000A
(if optional data size = 1)
0x000B
(if optional data size = 2)
0x000D
(if optional data size = 4)
Sequence
Counter
Incrementing counter to avoid replay
Part of the input data (byte 4 … 7)
D00A0000 (little endian representa-
tion of the counter value 00000AD0)
Security
Key
128 bit random key that is known
both to sender and receiver
3DDA31AD44767AE3CE56DCE2B3CE2ABB
Table 7 – Variable input parameters
