Patent ID: 7377433

Claim:
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 that generates a signal indicative of the sensed magnetic field; said signal comprising: at least a first signal portion having an amplitude less than a threshold; and at least a second signal portion having an amplitude greater than the threshold; an amplifier, wherein: the amplifier is in communication with the sensing unit; the amplifier amplifies the first signal portion by at least a first factor; the amplifier amplifies the second signal portion 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, that digitizes the amplified signal; a filter, in communication with the ADC, that attenuates the portion of the digitized signal indicative of the stored data; a data extraction unit, in communication with the ADC and the filter, that measures bit duration and peak location; and an authentication extraction unit, in communication with the filter and the data extraction unit, that extracts a set of scaled samples from the filtered and amplified first signal portion, the scaled samples representative of the remanent noise characteristic.