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cern that consumers may find the ap-
proach inconvenient.
We also show multimodal biomet-
rics can be integrated with mobile
devices in a user-friendly manner
and significantly improve their secu-
rity. In 2015, we thus implemented a
multimodal biometric system called
Proteus at California State University,
Fullerton, based on face and voice
on an Samsung Galaxy S5 phone, in-
tegrating new multimodal biometric
authentication algorithms optimized
for consumer-level mobile devices
and an interface that allows users
to readily record multiple biometric
traits. Our experiments confirm it
achieves considerably greater authen-
tication accuracy than systems based
solely on face or voice alone. The next
step is to integrate other biometrics
(such as fingerprints and iris scans)
into the system. We hope our experi-
ence encourages researchers and mo-
bile-device manufacturers to pursue
the same line of innovation.

Biometrics

Biometrics-based authentication es-tablishes identity based on physical and behavioral characteristics (such as face and voice), relieving users from having to create and remember secure passwords. At the same time, it challenges attackers to fabricate human traits that, though possible, is difficult in practice. 21 These advantages continue to spur adoption of biometrics-based authentication in smartphones and tablet computers.

Despite the arguable success of biometric authentication in mobile devices,

several critical issues remain, including, for example, techniques for defeating iPhone TouchID and Samsung Galaxy S5 fingerprint recognition systems. 2, 26 Further, consumers continue to complain that modern mobile biometric systems lack robustness and often fail to recognize authorized users. 4 To see how multimodal biometrics can help address these issues, we first examine their underlying causes.

The Mobile World

One major problem of biometric authentication in mobile devices is sample quality. A good-quality biometric sample—whether a photograph of a face, a voice recording, or a fingerprint scan—is critical for accurate identification; for example, a low-resolution photograph of a face or