Data verification method and magnetic media therefor

• US 5,235,166 A
• Filed: 02/14/1991
• Issued: 08/10/1993
• Est. Priority Date: 02/14/1991
• Status: Expired due to Term

• Current Assignee: XTec, Incorporated
• Original Assignee: XTec, Incorporated
• Inventors: Fernadez, Alberto J.
• Primary Examiner(s): PITTS, HAROLD I
• Application Number:
  US07/655,546
• Time in Patent Office: 908 Days
• Field of Search: 235/380, 235/449, 235/493
• US Class Current: 235/449
• CPC Class Codes: G06K 1/125 by magnetic means
• CPC Class Codes: G06K 5/02 the verifying forming a part of the marking action
• CPC Class Codes: G06K 5/04 Verifying the alignment of markings
• CPC Class Codes: G06K 7/084 sensing magnetic material by relative movement detecting flux changes without altering its magnetised state

Abstract

Magnetic media containing data and method for data verification are disclosed. The data verification method utilizes the relative position of specific features of magnetic media signals, such as, peak zero crossings, the ratio of preselected amplitudes, the locii of preselected points along the signal, the RMS value of the waveform and the like. In the preferred embodiment, the ratio of the separation of adjacent pulses in the signal is employed. The deviation of the precise location of the placement of the peak points in the signal waveform is referred to as "jitter". This "jitter" is enhanced to provide a pattern of "jitter" or a magnetic "signature" that is random, non-reproducible and that can be used to positively identify a particular specimen of magnetic media and the associated data. The magnetic jitter pattern or security signature can be separate from or an integral part of the data recorded on the magnetic media. The data verification method and magnetic media have particular application in the field of credit cards.

Claims

1. A method for generating a magnetic security signature on a magnetically recordable medium comprising the steps of:

A. producing a data representative signal to be recorded on said magnetically recordable medium; and

,

B. recording the data representative signal on the magnetically recordable medium while controlling the rate of change of the recording signal to extend the length of time that the magnetic flux transition remains on the most curved portion of the hysteresis loop of the magnetically recordable medium,

whereby the magnetic security signature is enhanced by increasing the hysteresis during the recording of the data representative signal.

2. The method of claim 1 further comprising the steps of:

A. determining a pattern of jitter in the recorded data representative signal;

B. generating data representative of said pattern of jitter; and

C. recording on said magnetically recordable medium said data representative of said pattern of jitter.

3. A method for identifying magnetically recordable medium having a data representative signal recorded thereon, said method comprising the steps of:

A. determining an existing pattern of jitter by precisely determining relative time positions of specific signal variations in at least a portion of the recorded data representative signal;

B. generating data representative of said existing pattern of jitter based on the determination of said relative time positions;

C. determining subsequently a subsequently existing pattern of jitter in said at least a portion of the recorded data representative signal;

D. generating data representative of said subsequently existing patter of jitter;

E. comparing the data representative of said existing pattern of jitter and data representative of said subsequently existing pattern of jitter; and

,

F. utilizing the results of said data comparison,

4. The method of claim 3 wherein said data representative of said existing pattern of jitter is recorded on the particular magnetically recordable medium so that the comparison of Step E is made between the recorded data representative of said existing pattern of jitter and said data representative of said subsequently existing pattern of jitter.

5. A method for generating a magnetic security signature on a magnetically recordable medium comprising the steps of:

A. pre-biasing the magnetically recordable medium by recording a pre-bias signal thereon that produces random saturated flux transitions on the magnetically recordable medium;

B. recording a data representative signal on the pre-biased magnetically recordable medium to produce a composite signal containing jitter with at least a portion of the jitter being attributable to the effect of the pre-biasing of the magnetically recordable medium; and

C. controlling during recording the rate of change of the recording data representative signal to extend the length of time that the magnetic flux transition remains on the most curved portion of the hysteresis loop of the magnetically recordable medium to further enhance the jitter,

whereby the magnetic security signature is enhanced by increasing the hysteresis during the recording of the data representative signal.

6. A method for generating a magnetic security signature on a magnetically recordable medium comprising the steps of:

A. pre-biasing the magnetically recordable medium by recording a pre-bias signal thereon that produces random saturated flux transitions on the magnetically recordable medium;

B. recording a data representative signal on the pre-biased magnetically recordable medium to produce a composite signal containing jitter with at least a portion of this jitter being attributable to the effect of the pre-biasing of the magnetically recordable medium;

C. controlling during recording the rate of change of the recording data representative signal to extend the length of time that the magnetic flux transition remains on the most curved portion of the hysteresis loop of the magnetically recordable medium to further enhance the jitter;

D. determining a pattern of the jitter in the composite signal;

E. generating data representative of said pattern of jitter; and

F. recording on said magnetically recordable medium said data representative of said pattern of jitter,

whereby the magnetic security signature is enhanced by increasing the hysteresis during the recording of the data representative signal.

7. A method for generating a magnetic security signature on a magnetically recordable medium comprising the steps of:

A. determining a pattern of jitter by precisely determining relative time positions of specific signal variations in a recorded data representative signal;

B. generating data representative of said pattern of jitter based on the determination of said relative time positions; and

C. recording on said magnetically recordable medium said data representative of said pattern of jitter.

8. A method for identifying magnetically recordable medium having a first data representative signal recorded thereon, said method comprising the steps of:

A. determining an existing pattern of jitter by precisely determining relative time positions of specific signal variations in at least a portion of the magnetically recordable medium in which the first recorded data representative signal is recorded;

B. generating data representative of said existing pattern of jitter based on the determination of said relative time positions;

C. writing a second data representative signal over the first data representative signal in said portion of the magnetically recordable medium to reflect a change of the data;

D. determining subsequent to the writing of said second data a subsequently existing pattern of jitter in said portion of the magnetically recordable medium; and

E. generating data representative of said subsequently existing pattern of jitter.

9. The method of claim 8 further comprising the steps of writing an additional data representative signal over the previously existing data signal each time a change of data occurs;

F. determining subsequent to each said writing of additional data a new existing pattern of jitter; and

G. generating representative data for each new existing pattern of jitter.

10. The method of claim 8 further comprising the step of encoding a signal representative said data representative of said existing pattern of jitter on a second portion of the magnetically recordable medium.

11. The method of claim 8 further comprising the step of encoding said data representative of said subsequently existing pattern of jitter.

12. The method of claim 10 further comprising the steps of redetermining the existing pattern of jitter prior to writing said second data representative signal;

retrieving the encoded signal; and

comparing the encoded signal and the redetermined existing pattern of jitter.