BLOCKING READER: DESIGN AND IMPLEMENTATION OF A ...

3.1 Introduction
CHAPTER 3
THEORY OF BLOCKING
In this chapter we will discuss about the theory behind Blocking. Previous
work from Juels, S.A. Wies and others came up with different approaches to provide
privacy and security to the RFID systems as discussed in section 1.4. Some concepts
and approaches like killer Tag, smart Tag are application specific, Tag jamming is
illegal and faraday’s cage has practical limitations. So in this thesis we have a new
approach to blocking called Blocker Reader where we block the Readers from reading
the Tag using Tag capture approach. This approach is similar to blocker tag but
here blocking reader acts like a Reader. An external device called Blocking Reader
captures your Tags and not allow other Readers to Read the Tag. In this chapter we
discuss the concept of Tag capture and see how the Blocking Reader use this to block
the Readers.
3.2 Inside a Passive RFID Tag
A passive UHF RFID Tag has no battery to power. It uses the carrier wave
power from the Reader to energize the circuitry and transmit the encoded ID. So the
Tags reply at the same frequency as the Reader. Tags antennas are hence designed
to be wide-band in 902-928MHz. Typically tuned to have maximum gain at center
frequency 915MHz.
Figure 3.1 shows some basic blocks that are present inside a passive Tag. Pas-
sive Tags now come as a single chip IC connected to an antenna. Inside the chip
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