Is an encrypted document definitely a privileged
document
If by "definitely" you mean to ask whether the fact, without more,
that the document is encrypted evidences that it is privileged, then:
No.
While that a document or other data file (whatever its format when
unencrypted) is encrypted indicates that its creator or other person
who encrypted it wanted to withhold its contents from persons to whom
s/he did not provide an unencrypted copy or decoding information, only
such a desire and intent does not alone support concluding that the
nature of the file or such a file's contents are "privileged" in the
sense that you evidently use that word here.
If during the discovery of a hard drive you find
damaging evidence in the form of a spreadsheet
adobe pdf document or word file would that
constitute a privileged document ??
Whether a document is/isn't "damaging" is a different issue from
whether it is immunized from discovery by reason of it being
privileged or immunized from later use at a trial because it is
privileged.
What if its in a password protected zip file and
you combinatorially gain access to the file ???
How did the you in question get access to the file? Did s/he secret
it away from the owner or other person entitled to its possession? Did
the file's creator or owner say to that you, in substance if not in
these exact words, "You may examine the contents of every file and
examine all other data on this hard disk including, if you find one or
more and if you then so decide, by using some 'brute force' numerical
means or other method of attempting to unencrypt/decode whatever if
any password protected file(s) that may be on the disk" ?
Whether or not there was no such explicit authorization, are there
facts about the communications concerning and other means by which the
you in question learned of the file(s) to which you refer on the basis
of which one ought or at least reasonably may conclude that, even if
the file would have been immune from examination by that you by reason
of some privilege if there were not such communications or other means
of learning of the files,, there has been a waiver of that privilege
in whole or in material part?
In sum, real world answers to your questions will depend on facts you
do not provide in your query.