NetKeys is a convenient application to print out ssh keys for sshd to consume. To pull keys from the directory, place the following in your sshd_config:

AuthorizedKeysCommandUser <some_dedicated_local_user>
AuthorizedKeysCommand /path/to/NetKeys --ID %u

Keep in mind that keys are not cached locally so if the network is partitioned then no keys will be available. Plan for this accordingly with backup keys.