Lim, Swee Hock

This thesis addresses a passive, economical strategy towards enhancing the security
feature of conventional plastic cards by embedding a set of electromagnetic (EM)
material that emulates an invisible "watermarking". It is an overlay strategy to prevailing
security measures.
Proposed method consists of incorporating (embedding) a set of metallic (foil-like) sheet
of high-mu material or high-conductivity metal, or a conducting-fiber interwoven fabric.
The test card when exposed to a suitable excitation of high frequency EM excitation
(with or without superimposing a static magnetic field), the plastic part yields a distinct
path-reluctance to the EM energy when compared to the embedded EM material section.
Sensing the resulting EM reaction with an appropriate circuit, delivers an output signal
depicting the presence of the embedded "watermarking" and any encoded signature in it.
The underlying concept is theoretically analyzed, relevant card-reading methods are
suggested and prototype (experimental) results are presented.