USER MANUAL
STM 550X / EMSIX
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ENOCEAN MULTI-SENSOR
© 2020 EnOcean | www.enocean.com F-710-017, V1.0
STM 550x / EMSIx User Manual | v1.0 | February 2020 | Page 36/79
5.3
STM 550x security implementation
STM 550x supports both standard and high security modes as defined by EnOcean Alliance.
The security mode can be selected both via the LRN button and via the NFC interface.
For high security mode, the default security level format (SLF) is set to use a 4 byte sequence
counter to generate a 4 byte signature.
For backwards compatibility with legacy systems, it is possible to select via NFC a legacy
mode using a 3 byte sequence counter to generate a 3 byte signature.
STM 550x will use secure chained telegrams (SEC_CDM) if high security mode is used and
the telegram payload (including rolling code and CMAC) exceeds 14 byte.