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Methods and apparatus for electronically storing and retrieving value information on a portable card

  • US 6,266,647 B1
  • Filed: 11/03/1997
  • Issued: 07/24/2001
  • Est. Priority Date: 11/03/1997
  • Status: Expired due to Term
First Claim
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1. A read/write unit for reading and writing information onto a solid-state medium, comprising:

  • a data authentication unit for reading and writing authentication information onto the medium, the data authentication unit programming data into each memory cell by applying a voltage which causes charges to be trapped in the memory cell, making a measurement of the level of trapped charges in the memory cell after the memory cell is programmed, generating a numerical representation of the level of trapped charges as a reference fingerprint of the memory cell, and storing the numerical representation, the data authentication unit being further operative to authenticate stored authentication information by comparing the reference fingerprint to numerical representations of a subsequent measurement of the levels of trapped charges in the memory cells defining an authentication fingerprint, in order to determine whether the data stored in the memory cells is authentic;

    a reading unit for reading information from the medium; and

    a writing unit for erasing previously written information from the medium and programming the medium with new information.

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