“The process goes like this: the second authentication factor is the proximity of the user’s phone to the computer being used to log in. Sound-Proof works even if the phone is in the user’s pocket or purse, and both indoors and outdoors.
“When the user logs in,” said the researchers, “the two devices record the ambient noise via their microphones. The phone compares the two recordings, determines if the computer is located in the same environment, and ultimately decides whether the login attempt is legitimate or fraudulent.””
Read more at phys.org.