Mobile devices often distribute measurements from a single physical sensor to
multiple applications using software-based multiplexing. On Android devices,
the highest requested sampling frequency is returned to all applications even
if other applications request measurements at lower frequencies. In this paper,
we comprehensively demonstrate that this design choice exposes practically
exploitable side-channels based on frequency-key shifting. By carefully
modulating sensor sampling frequencies in software, we show that unprivileged
malicious applications can construct reliable spectral covert channels that
bypass existing security mechanisms. Moreover, we present a novel variant that
allows an unprivileged malicious observer app to fingerprint other victim
applications at a coarse-grained level. Both techniques do not impose any
special assumptions beyond accessing standard mobile services from unprivileged
applications. As such, our work reports side-channel vulnerabilities that
exploit subtle yet insecure design choices in mobile sensor stacks.

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Author Of this post: <a href="">Carlton Shepherd</a>, <a href="">Jan Kalbantner</a>, <a href="">Benjamin Semal</a>, <a href="">Konstantinos Markantonakis</a>

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