USER MANUAL PREVIEW
PTM 535BZ
–
BLUETOOTH AND ZIGBEE GREEN POWER PUSHBUTTON TRANSMITTER
© 2021 EnOcean | www.enocean.com
F-710-017, V1.0
PTM 535BZ User Manual | v1.0 | May 2021 | Page 112/112
E.
Address resolution for resolvable private addresses (RPA)
PTM 535BZ provides the option to obfuscate its identity by means of using resolvable private
addresses (RPA that are generated using an Identity Resolution Key as described in
Chapter
. This appendix provides an example how to generate and resolve such address.
E.1
Address resolution example
We consider a PTM 535BZ module with the following 128 bit IRK:
IRK = BE759A027A4870FD242794F4C45220FB
We further consider a telegram with the following 48 bit resolvable private address:
RPA = 493970E51944
We will now test if this resolvable private address was generated using the IRK above.
Referring to the resolvable private address structure shown in
, we split the re-
solvable private address into
prand
and
hash
as follows:
prand = (RPA & 0xFFFFFF000000) >> 24
prand = 0x493970
hash = RPA & 0x000000FFFFFF
hash = 0xE51944
Next, we verify the address mode by checking the two most significant bit of
prand
:
mode = (prand & 0xC00000) >> 22
mode = 0b01
Referring to
Chapter 3.3.5.2
, the setting of
0b01
indicates resolvable private address mode.
To generate the hash, we add 104 bit of padding (all zeros) to
prand
:
padded prand = 0x00000000000000000000000000493970
We can now generate the hash as AES128 operation between IRK and
padded prand
:
hash = AES128(IRK; padded prand)
hash = AES128(0xBE759A027A4870FD242794F4C45220FB;0x00000000000000000000000000493970)
At the time of writing, a suitable online AES calculator could be found here:
http://testprotect.com/appendix/AEScalc
With this, we can calculate the result as:
hash = 0x286ACB1F9C8A80EE21B3F02225E51944
With that, we can verify that the lowest 24 bit of the calculated
hash
(
0xE51944
) match the
hash that was received as part of the resolvable private address. Therefore, the transmitter
of this telegram used this specific IRK to generate this resolvable private address.