Method and apparatus for authenticating a magnetic fingerprint signal using compressive amplification

• US 20050218229A1
• Filed: 12/17/2004
• Published: 10/06/2005
• Est. Priority Date: 07/22/1998
• Status: Active Grant

• Current Assignee: Washington University In St Louis
• Original Assignee: Washington University In St Louis
• Inventors: Morley, Robert E. Jr., Engel, George L., Richter, Edward J.
• Granted Patent: US 7,377,433 B2
• Time in Patent Office: Days
• US Class Current: 235/449
• CPC Class Codes: G06K 7/084 sensing magnetic material by relative movement detecting flux changes without altering its magnetised state
• CPC Class Codes: G06Q 20/347 Passive cards
• CPC Class Codes: G07D 7/004 using digital security elements, e.g. information coded on a magnetic thread or strip
• CPC Class Codes: G07F 7/08 by coded identity card or credit card or other personal identification means without personal verification means G07F7/02
• CPC Class Codes: G07F 7/0813 Specific details related to card security
• CPC Class Codes: G07F 7/12 Card verification

Abstract

A system for verifying the authenticity of data contained in a magnetic medium using the remanent noise characteristics of the magnetic medium. In one embodiment, the invention includes a sensing unit configured to generate a signal indicative of the sensed magnetic field and an amplifier. The amplifier is in communication with the sensing unit, is configured to amplify signals having amplitudes less than a threshold by at least a first factor and configured to amplify signals having amplitudes greater than the threshold by at most a second factor. The first factor is greater than the second factor. The invention also includes an analog-to-digital converter (ADC) in communication with the amplifier and configured to digitize the analog signal, a filter in communication with the ADC configured to attenuate the portion of the digitized signal indicative of the stored data, a data extraction unit in communication with the ADC and the filter, which is configured to measure bit duration and peak location and an authentication extraction unit in communication with the filter and the data extraction unit, which is configured to extract a set of scaled samples representative of the remanent noise characteristic.

Claims

1. A reader system for authenticating an object, the object comprising at least in part a magnetic medium including stored data and a remanent noise characteristic, the reader system comprising:

a sensing unit configured to generate a signal indicative of the sensed magnetic field;

an amplifier, wherein;

the amplifier is in communication with the sensing unit;

the amplifier is configured to amplify signals having amplitudes less than a threshold by at least a first factor;

the amplifier is also configured to amplify signals having amplitudes greater than the threshold by at most a second factor; and

the first factor is greater than the second factor;

an analog-to-digital converter (ADC) in communication with the amplifier and configured to digitize the analog signal;

a filter in communication with the ADC configured to attenuate the portion of the digitized signal indicative of the stored data;

a data extraction unit, in communication with the ADC and the filter, configured to measure bit duration and peak location; and

an authentication extraction unit, in communication with the filter and the data extraction unit configured to extract a set of scaled samples representative of the remanent noise characteristic.

2. The reader system of claim 1, wherein:

the amplifier is configured to amplify signals having amplitudes less than the threshold by the first factor;

the amplifier is also configured to amplify signals having amplitudes greater than the threshold by the second factor; and

the first factor is greater than the second factor.

3. The reader system of claim 2, where in the first factor is equal to or greater than 40 and the second factor is equal to or less than 6.

4. The reader system of claim 1 wherein the object comprises a magnetic stripe bearing card.

5. A method of authenticating an object, the object comprising at least in part a magnetic medium, the magnetic medium comprising stored data and a remanent noise characteristic, the method comprising:

generating a signal indicative of the magnetic field of the magnetic medium;

digitizing the signal;

preferentially amplifying portions of the signal having an amplitude less than a threshold;

filtering out the portions of the preferentially amplified signal that are indicative of the stored data; and

extracting a set of samples representative of the digitized remanent noise characteristic of the magnetic medium from the filtered signal.

6. The method of claim 5 wherein the gain applied to remanent noise characteristic component is equal to or greater than 40 and the gain applied to the data signal component is equal to or less than 6.

7. The method of claim 5, wherein the method comprises filtering the data signal component of the analog signal from the remanent noise characteristic component of the analog signal.