Patent ID: 6092193
Filing Date: 2000-07-18
Classification: H04L

Abstract:
A method for storage of digital data in a form so that subsequent alteration of that data can be detected, the method comprising:receiving a sequence of at least two distinct digital data values that relate to operation of an instrument, and representing each data value as an ordered sequence of alphanumeric characters;processing the sequence and expressing each data value as a plurality of usage data fields representing instrument usage data for a selected time interval: (1) a measure of usage of the instrument in the selected time interval; and at least one of (2A) an estimate of operating time that the instrument was operated within the selected time interval and (2B) an estimate of accumulated time the instrument was operated within the selected time interval at a usage level within a selected usage level interval;storing the instrument usage data field and at least one of the instrument operating time and the instrument accumulated time in a digital memory in separate locations;providing and storing a first error detection checksum for at least one selected usage data value in at least one of the usage data fields for the selected time interval at the time the at least one selected usage data value is stored interval memory;computing a second error checksum for the at least one selected usage data value, and comparing the first and second error checksums for the at least one selected usage data value; andwhen the first and second error checksums do not agree, interpreting this as indicating that at least one of the usage data fields for the selected time interval has been altered.