For decrypting KNX/IP Secure data, decryption keys must be defined. This is done via
Wireshark -> Menu -> Edit -> Preferences -> Protocols -> KNXnet/IP
Here, up to 10 decryption keys may be entered.
A decryption key consists of 16 bytes, and must be specified in hex.
A0 A1 A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF
Decryption keys may also be imported from a keyring.xml file exported from ETS.
This must still be tested with realistic keyring.xml files and corresponding test data.