In this assignment, you will select an open-source wearable medical device (hardware and software), perform threat modeling on it using the STRIDE method, and deliver the write-up. The deliverables for this module include:
- Threat Modeling document write-up
The device that I have chosen is as follows:
Jansen20 built an open-source desktop CT scanner
(see figure 1) for small objects. The complete design
files are available online,21 including the mechanical
design, circuit schematics and firmware. The CT
scanner uses a very low intensity radioisotope X-ray
source, which means that even low resolution images
take hours of measurement.22 It is designed for academic
and educational purposes, but the hope is that
it could eventually be used as a medical scanner in
developing countries.
Jansen designed the almost entirely laser-cuttable CT
scanner with four axes of motion, one being a large
rotary gantry. The stepper motor to rotate the gantry is
a National Electrical Manufacturers Association
(NEMA)17 stepper from open-source hardware distributor
Adafruit ($14), which transfers motion to the
drive shaft using a belt and timing pulleys. Each linear
axis has a small carriage that contains mounts for
either the source or detector. Each axis has an inexpensive
NEMA14 stepper also from Adafruit (under $14)
and an idler pulley.23 Jansen has used a very small solid
state high-energy particle detector called the type-5
from radiation watch, which can be connected to an
external microcontroller. The price of this particle
detector is just under $80.
To test out the motion and detector, Jansen put
together an Arduino shield ($45) with three Pololu
stepper controllers24 and a connector for the detector.
An SD card slot can store the image data for large scans.
The source of radiation used in Jansen’s design is
Barium-133 (cost between $80 and $125.00) with
80–383 KeV energy. This radioisotope check source is
sealed in epoxy, and is of such low intensity that it
not licensed25 and considered safe unless the material
is digested or taped to the body for long periods, and
it can be disposed of as general trash. The total cost
of Jansen’s open-source CT scanner (excluding the
laser cutter) is about $300. Open-source laser cutters
can be built for around $1000. All required components
are readily available and only basic knowledge
of electronics and laser cutting is required.
Attached is a sample write up of a similar document. Only the first two pages need to be done similar to the content and topics covered on those pages
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