Terrafrom has depricated the chef provissioner. We have been looking out to bootstarp the virtual machine using the keys insted og username and password as the baseline standards. We have tried multiple options given by chef in the documents and also discussed the same with chef support team. There is no such option to bootstrap the vm using the private key kept in some vault like Azure Valut or chef vault. We need to keep the private key in the local chef workstation in order to bootstrap the VM using key. So we are looking out of this feature.