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 losses. Consequently, the ability to reliably verify the authenticity of documents generally, and specifically of magnetic stripe cards is important.
Over the years, there have been numerous proposals for verifying documents, including the authenticity of magnetic stripe cards. A substantial number of prior proposals have been based on a concept of using certain magnetic characteristics of the magnetic stripe to identify cards. In that regard, it has been determined that generally, the magnetic stripes of individual cards possess inherent, substantially unique, remanent magnetic characteristics that can be repeatedly sensed. These characteristics have been recognized as contributing a noise-like component to sensed signals that is present in repeated sensings. Thus, along with the signal component representing recorded data, the repeatable noise-like signal component also appears. Just as the magnetic characteristics of individual stripes are distinct, the repeatable noise-like signals are virtually unique among cards. Accordingly, it has been proposed to employ such magnetic characteristics and the resulting repeatable noise-like signals (referred to as the “remanent noise characteristic”) as a basis for authenticating individual magnetic stripe cards. U.S. Pat. Nos. 5,365,586, 5,428,683, 5,546,462, 5,587,654, 5,625,689, 5,740,244, 5,920,628, and 5,959,794 (the disclosures of all of which are incorporated herein by reference) issued to Indeck et al. chronicle the invention of the use of remanent noise characteristics to authenticate various magnetic media. In addition, U.S. Pat. No. 6,098,881 issued to Deland et al., the entire disclosure of which is incorporated herein by reference, discloses using “relatively flat” portions representative of the remanent noise characteristics of the stripe that are located between magnetic transitions to authenticate individual documents.
A major consideration relating to the extensive use of magnetic characteristics for card recognition involves the number of cards in a system. For example, a typical reader must readily accommodate many billions of individual cards operating in combination with millions of individual processing units. In extensive systems, effectiveness and low error rate becomes exceedingly important, particularly in the realms of financial and security transactions, as are involved with bank cards.