Besides reducing the need for passcodes, fingerprints, facial recognition and other biometrics, the tool called EarEcho would be ideal for situations where users are required to verify their identity such as making mobile payments.
It could also eliminate the need to re-enter passcodes or fingerprints when a phone locks up after not being used.
EarEcho, which works when users are listening to their earbuds, is a passive system, meaning users need not take any action, such as submitting a fingerprint or voice command, for it to work, said Zhanpeng Jin, Associate Professor at the University at Buffalo in New York.
EarEcho uses modified wireless earbuds to authenticate smartphone users via the unique geometry of their ear canal.
When a sound is played into someone's ear, the sound propagates through and is reflected and absorbed by the ear canal all of which produce a unique signature that can be recorded by the microphone, said the study published in the journal Interactive, Mobile, Wearable and Ubiquitous Technologies.
"It doesn't matter what the sound is, everyone's ears are different and we can show that in the audio recording," Jin said.
"This uniqueness can lead to a new way of confirming the identity of the user, equivalent to fingerprinting," he said.
A prototype of the system proved roughly 95 per cent effective, the researchers said.
The research team built the prototype with off-the-shelf products, including a pair of in-ear earphones and a tiny microphone.
They developed acoustic signal processing techniques to limit noise interference, and models to share information between EarEcho's components.
The information gathered by the microphone is sent by the earbuds' Bluetooth connection to the smartphone where it is analysed.
To test the device, 20 participants listened to audio samples that included a variety of speech, music and other content.
EarEcho proved roughly 95 per cent effective when given one second to authenticate the subjects.
The score improved to 97.5 per cent when it continued to monitor the subject in three second windows, said the study.
( With inputs from IANS )