A quantum protocol is described which enables a user to send sealed messages
and that allows for the detection of active eavesdroppers. We examine a class
of eavesdropping strategies, those that make use of quantum operations, and we
determine the information gain versus disturbance caused by these strategies.
We demonstrate this tradeoff with an example and we compare this protocol to
quantum key distribution, quantum direct communication, and quantum seal
protocols.Comment: 10 pages, 2 figures. Third Feynman Festival, 25 -- 29 August 2006,
University of Maryland, College Park, Maryland, U.S.
