Can someone throw light on the differences between tokens and secret keys? I understand that "tokens" are crypto artefacts "introduced" into a system by an external party in order to authenticate whereas keys can be either generated on the device (for. eg a key pair in case of asymmetric cryptography & corresponding public key can be used externally to authenticate) or a secret symmetric key can be imported or generated on device and shared with an external party for authentication. Are tokens then "wrapped" secret keys? How are they structurally dfferent to keys( a string of random bits)?