Authentication of accumulated instrument data

Abstract

Methods and apparati for representing and storing a sequence of digital data values so that, once stored in memory, a data value cannot be modified, or cannot be modified without detection. Detection of subsequent data alteration may use error checksums, storage of instrument data in different data fields, data constraint relations, data encryption techniques and/or comparison of instrument identification numbers. Where data are to be stored in non-alterable form, the number of elements used in representing the sequence is reduced or minimized. A data value sequence can be supplemented by one or more additional data values that are received and similarly stored, without changing any of the sequence of data values already stored. The instrument data values can be individual readout values or can be accumulated sums of data values. Some of the methods are exact, allowing reconstruction of any data value with zero error. Other methods are approximate but are less complex to apply. These methods can be applied to numerical readout values from instruments such as odometers and electropotential meters at a selected sequence of sampling times.