<!--StartFragment-->7 Security considerations
QD presents an interesting challenge of balancing security and
openness. Many of the envisaged uses of QD require confidentiality of
the data . at the same time the receiver typically has no prior
knowledge of the sender or the sending user. This last point will
normally rule out all user-based authentication and access control.
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Comment: I don't think the receiver's lack of knowledge of the sender
necessarily rules out all user-based authentication. Authentication is
"the act of verifying the claimed identity of an individual,
station or originator".
Client-side certificates could be used for this. I think it's useful,
because it would allow one to set up a Printer that is publicly, but not
anonymously, accessible.
-Carl