This goes to show you that even a device's onboard LED can result in a security leak.
See article that details how researchers (white-hat hackers) have used video recordings to play back a reader's LED behavior to analyze it and 'read' the crypto keys it uses. The video below shows this firsthand.
******* *** ***** ** *** ****** fluctuates **** *** ******* *** ******* encrypted ****, *** ****** *** '*****' what *** *** ** *** *** color ******* *** ********* ** *** LED. *********** (*****-*** *******) *** ***** to **** **** *** *** ******** and ******* ** ** *** *** key.
*********, *** *********** ****** *** ********** and ***** ***** ******** *** ******** 378-bit ****. ** **** *** ******* shutter ** *** ********* ****** ** break *** *** *** ****** ** the *** ** ******** *** ****** key. *********** ******** **** **** **** 16 ****** (~** ****) ****.
**** ***** ***** *** *******:
*** *********** ****** *** ************* ** a '*********' ******, ********** **.** ***:
* ** *** **** ***** ******* are **********, *** **** *** ******* make ** *****, *** **** *** it ** * ****** ** ********** and *** **** ****** ** *** image.
* ** *** **** *** **** this ******* ***** ** ** ***** execute **** ***** ***** *** ****** to *** (******** ** *******: ****** ******* *****), *** ** ***** **** * fair ****** ** **** ************** ** get *** ****** **** *** **** use **** ** ***** **** * building ** *******, ***:
**** ***** ** ******* *** ****** patched **. ...*** ** *** ***** of ******* ***************, ******** ** *** ********** *** in * ****** ** *** **** not **** ***-******* ** ***.
*****/********?
* ******** ****** ********* ******* ***** ago ***** **** ****** **** * video ****** ******* ******* * ****** into * **** ** * ****** chip *** *** ***** ********* *** audio **** *** ********** ** *** bag. ***** **** ******* *** **** advance *********!