Entity
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... SIGs appear at the end of a request and authenticate the request with
the key of the submitting entity.
...
... KEY RRs that can authorize dynamic updates, i.e., entity or user KEY
RRs with the signatory field non-zero ...
... authenticated by dynamic keys
which expire, updates are transient in nature. Key rollover for an
entity that can authorize dynamic updates is more cumbersome since
the authority ...
... class, and signatory field flags as described below. In
addition, such KEY RRs must be entity or user keys and not have the
authentication use prohibited bit ...