User's Manual

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PTM 535BZ – BLUETOOTH AND ZIGBEE GREEN POWER PUSHBUTTON TRANSMITTER

3.4.2.1 Authentication implementation

PTM 535BZ implements data telegram authentication as described in IETF RFC3610 [4].

The 13 Byte Nonce (number used once – unique) initialization value is constructed as con-

catenation of 6 byte Source Address, 4 byte Sequence Counter and 3 bytes of value 0x00 (for

padding). Note that both Source Address and Sequence Counter use little endian format

(least significant byte first).

Figure 17 below shows the structure of the Nonce.

Figure 17 – Nonce structure

The Nonce and the 128 bit device-unique security key (by default SECURITY_KEY1, alterna-

tively SECURITY_KEY2) are then used to calculate a 32 bit signature of the authenticated

telegram payload shown in Figure 18 below.

LEN

0x0C

TYPE

0xFF

MANUFACTURER_ID

(Little Endian)

0xDA

SEQUENCE_COUNTER

(Little Endian)

INPUT_STATUS

AUTHENTICATED PAYLOAD

0x03 BYTE0 BYTE1 BYTE2 BYTE3 BYTE0

Figure 18 – Authenticated payload

The calculated 32 bit signature is then appended to the data telegram payload as shown in

Figure 14 in Chapter 3.4.1.

In addition to the RFC3610 standard [1] itself, please refer to Appendix D for a step-by-

step description of the authentication process.