移动终端自带传感器带来的隐 私新威胁   徐文渊   wyxu@zju.edu.cn 7/13/15   1   Privacy  is  not  a  new  concern   7/13/15   Source:  3M  privacy  filter  for  laptops  promo=onal  campaign   2   Smartphone Usage •  How many people use smartphones? Source:  Business  Insider   Source:  Gartner   •  Shipment of smartphone is increasing every year. Tablet   Mobile  Phone   2,250,000   2,000,000   Thousands  of  Units   75%  of  the  mobile  phones  are   smartphones  and  highly-­‐ featured  phones   PC(Desktop  &  Notebook)   1,750,000   1,500,000   1,250,000   1,000,000   750,000   500,000   250,000   0   2012   7/13/15   Reference：Anupam  Das   2013   2014   Year   2015   3   Smartphones  are  used  everywhere   Source:  mylookout.com   7/13/15   4   Privacy  expecta=ons  of  mobile  users   A Closer Look at Smartphones •  Today, smartphones come with a wide range of sensors. All of which are useful for a variety of tasks. • Mo=on  detec=on   • Gesture  detec=on   • Audio  Genre  detec=on   • Loca=on  detec=on   • Interac=on  with  nearby   devices   • Compass   7/13/15   Reference：Anupam  Das   6   Most  apps  use  mo=on  sensors   7/13/15   7   Most  apps  use  accelerometer   7/13/15   8   What can smartphone sensors do? 1.  Side channels for sensing environment 2.  Potential sources for device fingerprints. Should  sensors  be   accessed  freely? 7/13/15   9   Sensors:    Side  Channels 1.  Accelerometers   2.  Gyroscopes   7/13/15   10   (sp)iPhone:  Decoding  Vibra=ons   From  Nearby  Keyboards  Using   Mobile  Phone  Accelerometers     Philip  Marquardt,  Arunabh  Verma,   Henry  Carter  and  Patrick  Traynor   CCS2011     7/13/15   11   Decoding  Keyboards  Keystrokes  Using   Mobile  Phone  Accelerometers   7/13/15   12   Keystrokes  Sensed  by  Accelerometers Keystrokes 7/13/15   13   Keystrokes  Sensed  by  Accelerometers Single  char  “a” 7/13/15   Character  pair  “nm” Single  char  “I”   Character  pair  “pq” 14   A`ack  scenarios SMS,  hi   Alice Install  a  malicious  app 7/13/15   Record  accelerometer  data  and     recover  keystrokes 15   Results  （USA  Today） 7/13/15   16   Gyrophone:  Recognizing  Speech   From  Gyroscope  Signals   Anupam  Das,  Nikita  Borisov,   Ma`hew  Caesar   CCS  2014   7/13/15   17   Gyroscope  in  Smartphones •  Device used to measure or maintain orientation •  Works on the principals of angular momentum 微机电陀螺仪（MEMS） 7/13/15   18   微机电陀螺仪（MEMS） 7/13/15   19   Acous=c  Vibra=on •  Gyroscopes  are  sufficiently  sensi=ve  to  measure   acous=c  vibra=ons.     •  It  is  possible  to  recover  speech  from  gyroscope   readings;  turn  gyroscope  into  a  crude  microphone.     7/13/15   20