RFID explained
When non-tech savvy people think about security, they may
picture security cameras, guards, or even biometric security measures.
Cybersecurity professionals may think of firewalls or intrusion monitoring when
asked about their idea of security, and physical security is pushed to the
side. Recently, I’ve been testing the physical security measures of my employer
and one interesting thing I found is that RFID copying tools are available and
cost as little as 20 dollars. I purchased one of these tools and began testing
our RFID cards and, while it wasn’t able to copy our cards, it can be difficult
to understand. RFID may not be new, but it’s a complex technology that tends to
go unnoticed.
Radio Frequency Identification (RFID) utilizes
electromagnetic fields to track a corresponding device (card, tag, etc.). There
are two main kinds of RFID tags; active and passive. Passive tags do not have
their own power source, and pulls energy from the reader. Since the tag does
not have its own power source, it is short range and has a max distance of 25
meters, depending upon the device. They operate at a frequency range of 860-960
MegaHertZ (MHz). The costs of the tags tend to be cheap and range from 9 cents
to 20 dollars, however the readers can be very expensive in the hundreds of
dollars. These tags are typically used for item tracking or area control. (Note:
there are further subsets of passive tags, but for the sake of simplicity, they
will not be discussed at this time).
Active RFID tags use their own power source, so their range
is much greater with 30 to over 100 meters. These tags tend to only use 433 MHz
and are used in industries that involve vehicle traffic and identification. The
tags can be costly and range from 25 to 50 dollars each, and the readers can
cost in the hundreds.
Both active and passive RFIDs utilize different types of RFID
tags within the electromagnetic spectrum; low frequency, high frequency, and
ultra-high frequency. Low frequency operates at ranges of 30 – 300 kilohertz
(kHz). The reader range is very short for these with a max range of 10
centimeters. Since their signal is so weak, the cost for these tags is very cheap
and ranges from 9 cents to 5 dollars. Low frequency tags are part of the
passive tag type. High frequency has a max range of 13.56 MHz and a read range
of 30 centimeters. These tags cost a bit more with a range of 20 cents to 10
dollars and it is part of the passive tag type. Ultra-high frequency operates at
a frequency range of 300-3000 MHz. The read range and costs for these tags
tends to vary greatly, but it is typically qualified as active RFID tags.
RFID systems contain a variety of hardware, but every system
contains at least these three components: readers, antennas, and tags. RFID
tags, in its simplest form, contains two parts: an antenna for receiving and transmitting
signals and an RFID chip which stores the tag’s unique ID and other information
that can be tracked by the reader. Other information can include distance,
usage, or time stamps (though, time can be tracked by the reader as well). RFID
tags use the antenna to ‘ping’ a signal between the tag and the RFID reader.
Active tags use their own power source to generate these signals, but a passive
tag will use the signals generated by the reader to gain energy and send a
signal back. This energy activates the RFID chip, gathers the necessary
information, and transmits it back to the reader. There are different tags for
a variety of uses, but the most common card contains a chip with four memory
banks: EPC, TID, user, and reserved. Each of these memory banks contains
different types of information.
The RFID reader is the brain of the system. They transmit
and receive radio waves from tags in perform an action or give a response
depending upon the information received and the instructions it has been given.
There are two different types of readers: fixed and mobile. Fixed readers are
installed and stay in one location such as mounted on a wall or a door. Mobile readers
are handheld devices that communicate with a host computer. These readers are
typically used for temporary jobs such as construction sites or conventions.
RFID antennas convert the reader’s signal into radio-frequency
(RF) signals that are received by the tag. The antenna also converts the signal
sent by the tag into a format that the reader is able to understand. The reader’s
range depends upon the antenna and its polarity. Polarity refers to the plane the
antenna uses to give off RFID waves, which is either horizontal or vertical.
Different polarities are used for different RFID usages, for example, scanners
for semitrucks would use vertical polarity while an RFID reader used to access
a building would utilize horizontal polarity. There is a type of antenna that transmits
circular-polarized waves which constantly rotate between horizontal and
vertical, however, the cost of the hardware can be pricey, and the read range is
much shorter.
To summarize, the reader uses the antenna to send a signal
to the tag. The tag receives the signal and gathers information from its
onboard chip to create a signal to send back to the reader. The antenna
translates this signal to a format the reader can understand, and the reader
then activates its parameters depending upon the information contained in the
signal it received.
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