User's Manual

USER MANUAL
PTM 215B – 2.4 GHZ Pusbutton Transmitter Module
© 2016 EnOcean | www.enocean.com F-710-017, V1.0 PTM 215B User Manual | v0.8 | September 2016 | Page 23/42
2.10.1 Authentication implementation
PTM 215B implements telegram authentication based on AES128 in CCM (Counter with
CBC-MAC) mode as described in IETF RFC 3610.
The 10 Byte CCM Nonce (number used once – unique) initialization value is constructed as
concatenation of 48 bit Device ID and 32 bit Sequence Counter in little endian format (least
significant byte first.
Figure 16 below shows the AES128 Nonce.
Figure 16 – AES128 Nonce structure
The AES128 Nonce and the 128 bit device-unique security key are then used to calculate a
32 bit signature of the telegram payload shown in Figure 17 below.
Figure 17 – Authenticated payload
The calculated 32 bit signature is then appended to the payload as shown in
Figure 13 in chapter 2.9.6.1.