  Photo Response Non-Uniformity(PRNU) noise has proven to be very effective
tool in camera based forensics. It helps to match a photo to the device that
clicked it. In today's scenario, where millions and millions of images are
uploaded every hour, it is very easy to compute this unique PRNU pattern from a
couple of shared images on social profiles. This endangers the privacy of the
camera owner and becomes a cause of major concern for the privacy-aware
society. We propose SSS-PRNU scheme that facilitates the forensic investigators
to carry out their crime investigation without breaching the privacy of the
people. Thus, maintaining a balance between the two. To preserve privacy,
extraction of camera fingerprint and PRNU noise for a suspicious image is
computed in a trusted execution environment such as ARM TrustZone. After
extraction, the sensitive information of camera fingerprint and PRNU noise is
distributed into multiple obfuscated shares using Shamir secret sharing(SSS)
scheme. These shares are information-theoretically secure and leak no
information of underlying content. The encrypted information is distributed to
multiple third-part servers where correlation is computed on a share basis
between the camera fingerprint and the PRNU noise. These partial correlation
values are combined together to obtain the final correlation value that becomes
the basis for a match decision. Transforming the computation of the correlation
value in the encrypted domain and making it well suited for a distributed
environment is the main contribution of the paper. Experiment results validate
the feasibility of the proposed scheme that provides a secure framework for
PRNU based source camera attribution. The security analysis and evaluation of
computational and storage overheads are performed to analysis the practical
feasibility of the scheme.
