- Q: What is the Nike+iPod kit and how does it work?
A: The Nike+iPod kit consists of a sensor which is placed in the sole of
your left Nike+ shoe and a receiver which plugs into the bottom of the iPod
Nano. The sensor in your shoe detects when you take steps (while walking or
jogging) and transmits this information to the receiver.
When you start a workout session with the iPod, software on the iPod
collects the data from the sensor and keeps track of the distance you've walked
and the pace at which you're walking at. During a workout the iPod can provide
audio feedback about the time, distance, pace, or calories burned.
Once a workout is completed users can sync their iPod's with iTunes and
upload their data to the Nike+ website which contains software to track your
workouts, challenge other users to competitions, and set personal goals for you
- Q: How much does the Nike+iPod kit cost, and is it popular?
A: As for Nov 24, 2006, one can buy the Nike+iPod kit from the Apple online
store for $29 (USD). Apple has sold over 450,000 Nike+iPod kits, there are
currently 12 versions of the Nike+ shoe, and runners have logged almost 3
million miles on the Nike+ website.
- Q: Does the Nike+iPod kit reveal private information about a user?
A: Yes. When you walk or run the Nike+iPod sensor in your shoe will
transmit messages using a wireless radio. These messages contain a unique
identifier that can be detected from 60 feet away. This information is
potentially private because it can reveal where you are, even when you'd prefer
for a bad person to not know your location.
- Q: Why is it a problem if my Nike+iPod kit sensor transmits a unique
identifier when I walk or run?
A: The unique identifier can reveal your presence to nearby receivers.
Since the unique identifier doesn't change over time, someone could use the
sensor's broadcast messages to track which locations you visit, and when you
visit them. A bad person could use this information to compromise your personal
privacy and safety. We describe specific example scenarios, like stalking, in
- Q: Would it be hard to track someone?
A: No. It is easy to track someone who has a active Nike+iPod kit sensor in
We have built several mechanisms for detecting and tracking Nike+iPod shoe sensors.
- Windows XP-based surveillance devices:
We developed a mechanism for attaching a Nike+iPod receiver to a Windows
XP laptop via a USB port. When someone wearing an active Nike+iPod sensor
walks near one of our laptops, the laptop's attached Nike+iPod receiver will
detect the sensor's broadcast messages and will relay information about
those messages to the laptop. The laptop will then display the sensor's
unique identifier on the screen. The laptop will also use WiFi to upload
information about the observed sensor to a back-end database. This latter
step allows our Windows XP machines to serve as participating nodes in a
larger surveillance system.
- Gumstix-based surveillance devices:
We also made a cheap and small Nike+iPod surveillance device from
commercially available miniature gumstix computers. Our gumstix
surveillance devices also use WiFi to upload real-time surveillance data to
a back-end database, thereby allowing the gumstixs to serve as participating
nodes in a larger surveillance system.
The gumstix-based surveillance device is small enough to hide in the
environment, such as in the bushes near a running trail or under someone's
desk, and can detect nearby Nike+iPod sensors up to 60 feet away.
It would also be easy for anyone else to build their own gumstix-based
surveillance device, and the total cost for a full, WiFi-enabled gumstix
surveillance node is under $250 (USD). The node would be cheaper if one
prefers not to use the WiFi capabilities.
- Second-generation Intel Mote and Microsoft SPOT Watch:
We also built a Nike+iPod surveillance device using a second-generation
Intel Mote (iMote2) and the receiver that comes with the Nike+iPod Sport
Kit. We also wrote companion software for a Microsoft SPOT Watch.
Not only is the iMote2 another small surveillance device, but, because
of the SPOT Watch, our system will allow an adversary to obtain real-time
surveillance data on his or her wrist watch.
- Using and iPod as a surveillance device:
We also show how to convert a third-generation iPod into a surveillance
device. Such iPods are often available on eBay for around $100. Our iPod
surveillance device runs iPod Linux and our software, and has an attached
- GoogleMaps web application:
Recall that our Windows XP- and gumstix-based surveillance devices can
upload surveillance information to a back-end server in real-time. To
demonstrate what an adversary might do with that data, we created a
GoogleMaps-based tracking web application. This web application can overlay
surveillance data on a map in real-time, and can also display historical
tracking data on the map. Our back-end system can also email and SMS text
message tracking information to the adversary.
- Q: How much would it cost for someone to implement your surveillance
A: It depends on what that someone would like to do. Our gumstix prototype
shows that a bad person could build a full-featured, WiFi-enabled Nike+iPod
surveillance device for under $250. Adversaries desiring less functionality
could reduce the price of each surveillance device. Adversaries could also
significantly reduce the price of each surveillance node by custom building
nodes in bulk.
- Q: Would it be hard for someone to build their own surveillance system?
A: No, it would be neither hard nor expensive. Any hobbyist, including a
technically savvy teenager, could build their own surveillance device, assuming
that someone posted detailed instructions and the corresponding software on the
Internet (we currently do not plan to release our software). This person would
also need to perform a minimal amount of soldering (for our gumstix-based
surveillance device, this simply means soldering four wires).
- Q: How far away can you detect a Nike+iPod kit sensor?
A: 60 feet.
- Q: Can you detect my Nike+iPod sensor when I'm not working out?
A: Yes. As long as wearing an active Nike+iPod kit sensor and are walking or
- Q: Can you detect my Nike+iPod sensor even if I do not have my iPod with me.
A: Yes. As long as wearing an active Nike+iPod kit sensor and are walking or
- Q: Can't I just turn off the sensor when I'm not using it?
A: The sensor has an "on-off" button, but the Nike+iPod Sport Kit online
documentation says that "[m]ost Nike+iPod runners and walkers can just drop the
sensor in their Nike+ shoes and forget about it," and we believe this to be the
common case in practice.
- Q: Can't I just remove the sensor when I'm not using it?
A: Yes, the sensor can be removed from your shoe when you do not want to
workout. Additionally you can place the sensor under your front shoe laces to
make removal easier (or use a third party sensor holder to hold the sensor on
your shoe laces).
- Q: What can I do to improve my privacy if I want to use the Nike+iPod kit?
A: We strongly suggest turning off your Nike+iPod sensor when
you are not actively working out. Unfortunately, this suggestion
will only help you when you're not working out. If you want to
workout with the Nike+iPod kit, then we are unaware of any way to
improve your location privacy during your workout.
- Q: Could Apple have designed their system in a more privacy-preserving way?
A: Yes, there are simple cryptographic technique that the Nike+iPod designers
could have used to improve the privacy-preserving properties of the Nike+iPod
Sport Kit. But, as with any technical change, there will be some associated
tradeoffs, like sensor battery life, manufacturing costs, and use experience.
See Section 6 of the technical report below for more information.
- Q: Will you be releasing your software?
A: We currently do not plan to release our software.