Generating Forms Key with Flow or Apex

From Version 6.7+, you can use APEX and FLOWS to generate the b3f__Form?key={PARAM}. You can use the Key parameter to pre-populate a form, while obfuscating the url parameters.

Apex

Object resp = FormsLinkManager.getFormKey(new List<FormsLinkManager.Request>{
    new FormsLinkManager.Request('FORM_ID', 'RECORD_ID', 'VERSION_ID')
});
//Note: Record Id and Version id are optional. Leave as null if not needed
system.debug('Rsp: ' + resp);

Flows

Use the "Get Forms Key" Invocable Action