Hacking_and_Penetration_Testing_with_Low_Power_Devices

Power requirements
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the city and highway, respectively. Today, you cannot buy a US automobile that achieves anywhere
close to that mileage (not even a hybrid).
The automakers have not been motivated by the government to produce more efficient vehicles.
The American consumers that continue to buy SUVs despite being faced with gasoline prices that
have doubled and at times tripled under the Obama administration are not providing automakers
much incentive to produce more efficient vehicles.
In a similar way, the computer manufacturers are not motivated to produce more efficient systems.
Neither the government nor consumers are providing incentive for companies to create more
efficient systems. Additionally, manufacturers have made a concerted effort to convince everyone
that they need the most powerful computer system available. Software companies such as Microsoft
with ever-growing (bloating?) products have not helped this situation. As a result of all this, people
feel they need six processor cores, a high-performance graphics card, and at least 8 GB of RAM to
browse the Web, edit documents, and send e-mail.
It is time to drill down a bit and get more specific on the power requirements for
the Beagles. We will focus on the BeagleBone Black for this discussion as it is the
most likely platform to be deployed by readers of this book. According to the
BeagleBone Black System Reference Manual, the BeagleBone Black will consume
200-480 mA of current at 5 V. This corresponds to 1-2.4 W of power.
The numbers above include the power required by a complete system. The test
configuration used involved a device connected to an HDMI monitor, USB hub,
4 GB flash drive, Ethernet, and serial debugger. In other words, this is a worst case
scenario. Based on my experience and reports from a number of others, we will use
an average current of 220 mA for a highly loaded BeagleBone Black with no monitor
or debugger attached. The methods for reducing power consumption will be discussed
later in this chapter.
Power consumption of peripherals such as LCD displays and IEEE 802.15.4
radios will be discussed in greater detail later in this book. For now, we are most
concerned about power requirements for remotely deployed drones. These drones
will likely not sport LCD displays. The IEEE 802.15.4 radios will not be operated
continuously, and thus, estimating their power consumption becomes a bit more
difficult.
A drone installed outside of a penetration test target’s facility will likely need to
utilize wireless networking. A wireless adapter will require power to continuously
receive and occasionally transmit packets. A typical wireless adapter found in a laptop
computer has a transmit power of around 15 dBm, which corresponds to 0.032 W
or 6 mA of current at 5 V. Allowing for power to operate a receiver and other circuitry
if we quadruple this current, we are still under 25 mA of additional current.
The Alfa AWUS036H USB wireless adapter is very popular among hackers. It
has an output power of 1 W. At 5 V, this means the Alfa would require 200 mA just
to transmit, plus additional power to operate the receiver and other circuitries, that is,
if the Alfa was 100% efficient, which it is not. In reality, the Alfa can require up to
500 mA of current while transmitting. The methods of reducing this power consumption
will be discussed later in this chapter. A good number to use for average current
requirements after implementing these power-saving measures is 60 mA.