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Brief Full Advanced Search Search Tips (Publisher: John Wiley & Sons, Inc.) Author(s): Bruce Schneier ISBN: 0471128457 Publication Date: 01/01/96 Search this book:
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----------- Chapter 4 Intermediate Protocols
4.1 Timestamping Services
In many situations, people need to certify that a document existed on a certain date. Think about a copyright or patent dispute: The party that produces the earliest copy of the disputed work wins the case. With paper documents, notaries can sign and lawyers can safeguard copies. If a dispute arises, the notary or the lawyer testifies that the letter existed on a certain date. In the digital world, it’s far more complicated. There is no way to examine a digital document for signs of tampering. It can be copied and modified endlessly without anyone being the wiser. It’s trivial to change the date stamp on a computer file. No one can look at a digital document and say: “Yes, this document was created before November 4, 1952.” Stuart Haber and W. Scott Stornetta at Bellcore thought about the problem [682, 683, 92]. They wanted a digital timestamping protocol with the following properties: — The data itself must be timestamped, without any regard to the physical medium on which it resides. — It must be impossible to change a single bit of the document without that change being apparent. — It must be impossible to timestamp a document with a date and time different from the present one. Arbitrated Solution This protocol uses Trent, who has a trusted timestamping service, and Alice, who wishes to...
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