Authentication of accumulated instrument data

• US 6,092,193 A
• Filed: 05/29/1997
• Issued: 07/18/2000
• Est. Priority Date: 05/29/1997
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Janky, James M., Gildea, David R., Schipper, John F., Loomis, Peter V. W.
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/865,271
• Time in Patent Office: 1,146 Days
• Field of Search: 380/23, 380/20, 705/28, 702/155, 713/168, 713/193
• US Class Current: 713/193
• CPC Class Codes: H04L 2209/20 Manipulating the length of blocks of bits, e.g. padding or block truncation
• CPC Class Codes: H04L 2209/84 Vehicles
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions

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.

Claims

1. 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; and

when 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.

2. The method of claim 1, further comprising:

selecting said instrument to provide a measure of distance traveled by a vehicle on which said instrument is mounted; and

selecting said measure of usage to be a measured distance traveled by the vehicle.

3. A method for storage of digital data in a form so that subsequent alteration of that data can be detected, the method comprising the steps of:

storing an initial value of a sum of data value increments in unencrypted form and in encrypted form;

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;

accumulating a series of received data values as a data value increment;

when the value of the data value increment exceeds a selected threshold value, (1) adding the data value increment to the sum of values in unencrypted form and storing the resulting sum as a data value sum in unencrypted form, and (2) adding the data value increment to the sum of values in encrypted form and storing the resulting sum as a data value sum in encrypted form;

comparing the value of at least one data value sum in unencrypted form to the value of the corresponding decrypted value of the data value sum stored in encrypted form; and

when the value of the at least one data value sum in unencrypted form and the value of the corresponding data value sum in encrypted form do not substantially agree with each other, indicating that at least one of the data value sums in unencrypted form may have been altered.

4. The method of claim 3, further comprising selecting said digital data values to represent trip mileage for a selected trip, as determined by a vehicle odometer.

5. A method for storage of digital data in a form that cannot be subsequently altered, the method comprising:

receiving a sequence of at least two distinct digital data values, and representing each data value as an ordered sequence of at most M+1 integers, with each integer lying in a selected interval of integers, where M is a selected positive integer;

selecting an intermediate delimiter sequence D of integers drawn from a selected collection of characters and an end delimiter sequence E of integers drawn from the selected collection of characters, where the sequence of characters representing the delimiter sequence D and the sequence of characters representing the delimiter sequence E differ from each other and from all possible sequences of integers representing a data value;

storing a sequence of integers representing each data values in a memory having a plurality of memory elements as a concatenated sequence of integers, where each two consecutive data value sequences are separated by at least one intermediate delimiter sequence, where a memory element cannot be altered after the memory element is initially activated; and

placing a selected end delimiter after a last data value in the sequence of the data values, where the end delimiter is a sequence of Q alphanumeric characters, the end delimiter sequence is not found in any sequence representing a data value, the intermediate delimiter sequence is a sequence of R alphanumeric characters, and Q and R are selected positive integers satisfying Q+1≦

R.

6. The method of claim 5, further comprising:

selecting said end delimiter sequence to be a sub-sequence of Q consecutive alphanumeric characters in said intermediate delimiter sequence.

7. The method of claim 5, further comprising selecting said digital data values to represent trip mileage for a selected trip, as determined by a vehicle odometer.

8. A method for storage of digital data in a form that cannot be subsequently altered, the method comprising:

receiving a sequence of at least two distinct digital data values, and expressing each data value as an ordered sequence of M alphanumeric characters, from a least significant character to a most significant character, where M is a selected integer greater than 1;

for a selected positive integer M2 that is less than or equal to M, representing each data value by an ordered approximate sequence of M2 consecutive characters drawn from the ordered sequence of M characters representing the data value;

separating any two consecutive approximate sequences representing data values by a selected intermediate delimiter sequence that is an ordered sequence of alphanumeric characters and the intermediate delimiter sequence is not found in any approximate sequence representing a data value;

storing at least two consecutive approximate sequences representing data values and an intermediate delimiter sequence separating the two approximate sequences in a memory having a plurality memory elements, with each memory element representing an alphanumeric character, where a memory element cannot be altered after the memory element is initially activated; and

placing a selected end delimiter after a last data value in the sequence of the data values, where the end delimiter is a sequence of Q alphanumeric characters, the end delimiter sequence is not found in any approximate sequence representing a data value, the intermediate delimiter is a sequence of R alphanumeric characters, and Q and R are selected positive integers satisfying Q+1≦

R.

9. The method of claim 8, further comprising:

selecting said end delimiter sequence to be a sub-sequence of Q consecutive alphanumeric characters in said intermediate delimiter sequence.

10. The method of claim 8, further comprising selecting said integer M2 to be equal to M.

11. The method of claim 8, further comprising selecting said integer M2 to be no larger than M-1.

12. The method of claim 8, further comprising selecting said digital data values to represent trip mileage for a selected trip, as determined by a vehicle odometer.

13. Apparatus for storage of digital data in a form so that subsequent alteration of that data can be detected, the apparatus comprising:

a computer that is programmed;

to store an initial value of a sum of data value increments in unencrypted form and in encrypted form;

to receive a sequence of at least two distinct digital data values that relate to operation of an instrument, and to represent each data value as an ordered sequence of alphanumeric characters;

to accumulate a series of received data values as a data value increment;

when the value of the data value increment exceeds a selected threshold value, (1) to add the data value increment to the sum of values in unencrypted form and storing the resulting sum as a data value sum in unencrypted form, and (2) to add the data value increment to the sum of values in encrypted form and storing the resulting sum as a data value sum in encrypted form;

to compare the value of at least one data value sum in unencrypted form to the value of the corresponding decrypted value of the data value sum in encrypted form; and

when the value of the at least one data value sum in unencrypted form and the value of the corresponding data value sum in encrypted form do not substantially agree with each other, to indicate that at least one of the data value sums in unencrypted form may have been altered.

14. Apparatus for storage of digital data in a form so that subsequent alteration of that data can be detected, the apparatus comprising:

a computer that is programmed;

to store an initial value of a sum of data value increments in a memory;

to receive a sequence of at least two distinct digital data values that relate to operation of an instrument, and to represent each data value as an ordered sequence of alphanumeric characters;

to accumulate a series of received data values as a data value increment;

when the value of the data value increment exceeds a selected threshold value, (1) to add the data value increment to the sum of values to form a resulting new sum of values, (2) to compute at least one error checksum for the new sum value, (3) to store the new sum value and the at least one error checksum;

to compute an error checksum for at least one stored data value sum and to compare the computed error checksum with a corresponding stored error checksum for the stored data value sum; and

when the computed error checksum and the stored error checksum do not substantially agree with each other, to indicate that at least one of the data value sums has been altered.

15. Apparatus for storage of digital data in a form that cannot be subsequently altered, the apparatus comprising:

a computer that is programmed;

to receive a sequence of at least two distinct digital data values, and to represent each data value as an ordered sequence of at most M+1 integers, with each integer lying in a selected interval of integers, where M is a selected positive integer;

to select an intermediate delimiter sequence D of integers drawn from the selected interval of integers and an end delimiter sequence E of integers drawn from the selected interval of integers, where the sequence of integers representing the delimiter sequence D and the sequence of integers representing the delimiter sequence E differ from each other and from all possible sequences of integers representing a data value; and

to store a sequence of integers representing each data values in a memory having memory elements as a concatenated sequence of integers, where each two consecutive data value sequences are separated by at least one intermediate delimiter sequence, where a memory element cannot be altered after the memory element is initially activated.

16. Apparatus for storage of digital data in a form that cannot be subsequently altered, the apparatus comprising:

a computer that is programmed;

to receive a sequence of at least two distinct, increasing digital data values, and to represent each data value as an ordered sequence of M alphanumeric characters, where M is a selected integer greater than one;

to represent each data value after the first data value in the sequence by a truncated sequence of at least M1 consecutive alphanumeric characters used to represent the data value by the M alphanumeric characters, where M1 is a selected positive integer that is less than M, where the truncated sequence representing the data value is the M1 least significant characters representing the data value in the ordered sequence of M characters and the remaining M-M1 characters in the ordered sequence have all been determined by one or more preceding members of the sequence of data values;

to separate any two consecutive truncated sequences representing data values by a selected intermediate delimiter that is an ordered sequence of alphanumeric characters and the intermediate delimiter sequence is not found in any sequence representing a data value; and

to store at least two consecutive truncated sequences representing data values and an intermediate delimiter separating the two truncated sequences in a memory having a plurality memory elements, with each memory element representing an alphanumeric character, where a memory element cannot be altered after the memory element is initially activated.

17. Apparatus for storage of digital data in a form that cannot be subsequently altered, the apparatus comprising:

a computer that is programmed;

to receive a sequence of at least two distinct digital data values, and expressing each data value as an ordered sequence of M alphanumeric characters, from a least significant character to a most significant character, where M is a selected integer greater than 1;

for a selected positive integer M2 that is less than or equal to M, to represent each data value by an ordered approximate sequence of M2 consecutive characters drawn from the ordered sequence of M characters representing the data value;

to separate any two consecutive approximate sequences representing data values by a selected intermediate delimiter sequence that is an ordered sequence of alphanumeric characters and the intermediate delimiter sequence is not found in any approximate sequence representing a data value; and

to store at least two consecutive approximate sequences representing data values and an intermediate delimiter sequence separating the two approximate sequences in a memory having a plurality memory elements, with each memory element representing an alphanumeric character, where a memory element cannot be altered after the memory element is initially activated.