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 63/68
B.4
Variable internal parameters
The RFC3610 implementation in PTM 215B derives four internal parameters – Nonce, A0,
B0 and B1 – based on the telegram specific input data and the constant internal parame-
ters.
These variable internal parameters - listed in Table 9 below - are then used together with
the security key to calculate the actual signature.
Parameter
Comment / Description
Example
Nonce
13 byte initialization vector based on
concatenation of source address, sequence
counter and padding, see 4.8.1
FE19000015E2D00A0000000000
A0
A0_Flag
followed by
Nonce
followed by 2 byte
0x00
01FE19000015E2D00A00000000000000
B0
B0_Flag
followed by
Nonce
followed by 2 byte
0x00
(no message to encode)
49FE19000015E2D00A00000000000000
B1
Input Length
followed by I
nput Data
fol-
lowed by 5 / 4 / 3 / 1 byte of
0x00
padding
(for optional data size = 0 / 1 / 2 / 4 byte)
00090CFFDA03D00A0000030000000000
Table 9 – Variable internal parameters
B.5
Algorithm execution sequence
The algorithm uses the variable internal parameters
A_0
,
B_0
,
B_1
together with the private
key to generate the authentication vector
T_0
using three AES-128 and two XOR opera-
tions. The algorithm execution sequence is shown in Figure 32 below.
The first four bytes of
T_0
are then used to authenticate PTM 215B telegrams.
Figure 32 – Authentication algorithm sequence