Guessing Smart Phone PINs by Monitoring the Accelerometer

https://www.schneier.com/blog/archives/2013/02/guessing_smart.html

In controlled settings, our prediction model can on average classify the PIN entered 43% of the time and pattern 73% of the time within 5 attempts when selecting from a test set of 50 PINs and 50 patterns. In uncontrolled settings, while users are walking, our model can still classify 20% of the PINs and 40% of the patterns within 5 attempts.