Method and apparatus for authenticating a magnetic fingerprint signal using a filter capable of isolating a remanent noise related signal component

#The present invention relates generally to systems and processes involving the utilization of repeatable magnetic stripe characteristics to authenticate magnetic stripe-bearing documents.

#Various forms of cards bearing a magnetic stripe (e.g., magstripe cards) have long been used for a variety of different purposes. Such cards are currently used in large numbers, for example in the forms of credit cards, debit cards, transportation/transit/airline tickets, I.D. cards and so on. Typically the magnetic strips/stripes (also referred to as the magstripes) of such cards carry recorded data relating to the use of the card, and in some instances relating to the assigned user or owner of the card.

#Although magnetic stripe cards are widely and successfully used in commerce and industry, counterfeiting and modification of cards (along with other forms of documents) are common occurrences, resulting in great monetary losses. Consequently, the ability to reliably verify the authenticity of documents generally, and specifically of magnetic stripe cards is important.

#In the drawings, like reference characters generally refer to the same parts throughout the different drawings.

#FIG. 1 illustrates an embodiment of a magstripe card reader system in accordance with aspects of the invention;

#FIG. 2 is a graphic representation of a portion of a typical format of a track 200 of the magnetic stripe 155 as shown in FIG. 1;

#FIG. 1 illustrates an embodiment of a magstripe card reader system in accordance with aspects of the invention. The magstripe card reader system 100 comprises a sensing unit 105, a compressive amplifier 110, a selectable bandwidth ADC 115, a controller 120, a data extraction unit 125, a filter 130, an authentication extraction unit 135, an encryption unit 145, and a data combiner 140. A transaction unit located outside of the reader system 100, such as at a bank or its processor, receives the data produced by the reader system 100.

#In one embodiment, the sensing unit 105 reads the magnetic stripe 155 of a card 150. The analog signal 160 produced by the sensing unit 105 includes a signal indicative of the card data and a remanent noise characteristic signal. As previously mentioned, the card data includes the account-related data that can be easily forged. On the other hand, the remanent noise characteristic is repeatable, deterministic, and virtually unique for a given magnetic medium that serves as an authenticity identifier for the magnetic medium. The remanent noise characteristic is very difficult to forge. The analog signal 160 amplified by the compressive amplifier 110, which preferentially amplifies the remanent noise characteristic signal component over the recorded data signal component. More specifically, the compressive amplifier 110 amplifies the remanent noise signal component with a greater gain than that with which it amplifies the recorded data signal component. The preferentially amplified analog signal 165 is then provided to the selectable ADC 115 for conversion and subsequent digital processing.

#The selectable ADC 115 provides analog to digital conversion with variable bandwidths and sampling rates based on the swipe speed of the card 150 at the sensing unit 105. To provide variable bandwidths and sampling rates, the selectable ADC 115 receives bandwidth and sampling rate select data from a controller 120, which is in communication with the data extraction unit 125. The digital signal produced by the selectable ADC 115 is provided to the data extraction unit 125 and the high pass filter 130.