USER MANUAL
STM 550 / EMSI
–
ENOCEAN MULTISENSOR FOR IOT APPLICATIONS
© 2020 EnOcean | www.enocean.com F-710-017, V1.0
STM 550 / EMSI User Manual | v1.3 | September 2020 | Page 35/97
6
Security
STM 550 implements the security handling functions as specified in the EnOcean security
specification:
https://www.enocean-alliance.org/sec/
6.1
Basic concepts
Security for radio transmission addresses two main issues:
◼
Unauthorized interception (reception and correct interpretation) of transmitted data
In doing so, a third (unauthorized) party is able to understand the content of a re-
ceived content.
◼
Unauthorized transmission of radio telegrams
In doing so, a third (unauthorized) party is able to transmit a radio telegram that is
treated by a receiver as valid request.
Somewhat loosely speaking, the goal of security has to be preventing an unauthorized person
(often referred to as an
Attacker
) both from learning about the current state of a system and
from actively changing it.
These goals can be achieved via techniques such as telegram encryption, telegram authori-
zation and dynamic security key modification. All three techniques will be reviewed in the
subsequent chapters for reference.
6.1.1
Telegram encryption
The goal of telegram encryption is to prevent unauthorized receivers from correctly inter-
preting the content of a telegram.
In order to do so, the original (plain text) data is
encrypted
with a
key
thus transforming it
into encrypted, unreadable data. Only when the correct key is known it is possible to trans-
form
–
decrypt
- the encrypted data into readable data again. Figure 22 below shows the
concept.
Figure 22
–
Telegram encryption
Decryption
Decryption Key
Unencrypted Data
(Plain Text)
Encryption
Unencrypted Data
(Plain Text)
Encrypted Data
Encryption Key
Encrypted Data
