Digital Forensics in Small Devices: RFID Tag Investigation

An electronic chip connects to the antenna in order to receive or transmit the
signal. According to Sanghera et al., (2007, p. 53), the tag consists of “a logical
unit which is used for implementing protocol for tag-reader communication”,
“memory which is used for storing data”, “a modulator which is used for
modulating the outgoing signal and demodulating the incoming signal”, and
“power controller which is used for converting alternate current (AC) power from
the incoming signal to direct current (DC) power supply and supplying power to
the components of the chip.”
The purpose of the antenna on the chip is to receive a signal from the
antenna of the reader and vice visa. It is important to note that the position and
design of the antenna determines the range or coverage communication zone
between the tag and the RFID reader (Ngai et al., 2008). The substrate for RFID
tags accommodates the antenna and the chip.
Depending on whether or not has an on-tag power source (that is a battery),
RFID tags are classified into passive, semi-passive and active types. Generally,
passive tags which do not have an on-tag power source are read-only (RO) while
semi-passive and active tags that have an on-tag power source are Read/Write or
Smart tags (Hunt et al., 2007; Xiao et al., 2007; Sanghera et al., 2007). As the tags
come in different types and classes; the way they operate, their size, cost and
characteristics are also dissimilar. According to the use of radio frequencies, the
RFID tag technologies are classified into microwave, ultra high frequency (UHF),
high frequency (HF) and low frequency (LF) RFID tags. Similarly, based on the
functionality of the tag; there are six tag classes (starting from Electronic Product
Code: EPC Class 0 to Class 5) proposed by Auto-ID Centre, Massachusetts
Institute of Technology. Sanghera et al., (2007, pp. 61-65) describe the different
classes of RFID tags as follow:
“The Class 0 tags are passive and RO tags which normally programme
with a unique number during manufacturing. Likewise, the Class 1 and Class 2
tags are passive and write once/read many (WORM) memory tags, and have 128-
bit and 65KB of memory space respectively. However, the Class 3 tags are re-
writable (can be programmed and reprogrammed by the user many times), semi-
passive tags as they have got their own power sources on-tag for supporting a
longer read range and have 56KB of memory space. But, they are not capable of
initiating communication with the reader.
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