Exploring the Constrained Application Protocol (CoAP) in Wireshark.
wireshark golioth_basics_psk.pcapng
The Golioth Basics (PSK) example uses the Golioth Basics program from the Golioth Firmware SDK at v0.7.0.
In order to decrypt CoAP messages, the pre-shared key must be supplied in hex form. The following PSK can be used for the provided capture.
3639616631363835626139303830626539303739323237323863316539376335
It should be supplied in the Pre-Shared Key field in Wireshark under Edit > Preferences > Protocols > DTLS as shown below.
To convert your own PSK to hex form, use the following command:
echo -n "YOUR_PSK_HERE" | xxd -ps -c 32