De-Crypt messages using GXDLMS?

Hi Guys,
I would like to decrypt and read the serial stream coming from my power measuring device "Kaifa MA309".
I have connected a MBUS-USB Adapter to read the serial stream but unfortunately it is crypted with a static code. I got the code from my power supplying company but unfortunately it is using GXDLMS and I have no idea how to decrypt this in Node-Red.
Is there a library ? Is there a simple XOR I have to apply on the stream or how is this done ?
The Key is simply a HEX-String like this: 36C66639E4867B328A32234B282A793BBB

Can someone give me a hint where to start ?

BR
G