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Trusted timestamping is the process of securely keeping track of the creation and modification time of a document. Security here means that no one—not even the owner of the document—should be able to change it once it has been recorded provided that the timestamper's integrity is never compromised.
The term "timestamp" derives from rubber stamps used in offices to stamp the current date, and sometimes time, in ink on paper documents, to record when the document was received. Common examples of this type of timestamp are a postmark on a letter or the "in" and "out" times on a time card .
The postmarks bore the initial of the particular post office or handling house it was sent from along with a separate time stamp. Postage was prepaid and the postmark was applied to the mailed item by means of an inked hand-stamp. Some historians also consider these postmarks to be the world's first postage "stamps". [3]
The experience sampling method (ESM), [1] also referred to as a daily diary method, or ecological momentary assessment (EMA), is an intensive longitudinal research methodology that involves asking participants to report on their thoughts, feelings, behaviors, and/or environment on multiple occasions over time. [2]