Within the Postman Pre-Request script section, very usefull to prepare data before the actual Rest API call, it seems totally impossible to create a standard signature for a JWT structure.
A super-mandatory step if you want to correctly sign the token or in general a message with your own private key before sending it in the request.
Ok that Postman support the ‘crypto-js’ library for crypto stuff, but it does not look like a full version with all the (security) standard functionalities that are required of an API client. And it seems there are not other options since it seems impossible to import other (external) modules within the nodejs runtime used by Postman, nor to include/import other js libraries that easily fulfil the purpose.
So it’s really a dead end, and a bad one since we are talking about security standards for APIs related to JWT tokens.
Please help 