Exisitng Symmetric HS512 secret key based Tokens

I have a series of API services that consume JWTs that are signed (with HS512 with a simple secret key using jjwt) within the services and now we’re moving to Keycloak V24. Is there anyway as it stands to use the same signing done so that the services remain intact and operational.

The old services have duplicated the code to sign and verify so it is a heavy duty just to change that. So my question is if within Keycloak we could use the same signing key and secret to generate the tokens? If Yes. Some guidance on how to achieve this.