Escaping a string to unicode lowercase hex digits

[pachocastillosr]

Hi,

I am trying to validate a signature from Whatsapp Webhooks. Docs say the following:

I already got the raw text of the payload.

How can I escape this raw text into “lowercase hex digits”?

I have tried using the Toolbox plugin like this:

And this (got this code from a StackOverflow thread that supposedly solved this problem):

None of this codes have worked yet. Any suggestions?