Secure image databases through distributed source coding of SIFT descriptors

The adoption of distributed databases calls for storing data at two or more sites, in order to address application-specific requirements including, e. g., redundancy, data locality, and so on. When visual data (including images, videos and their corresponding descriptors) need to be stored, synchronization across different sites might require significant bandwidth resources. In this paper we explore the use of distributed source coding to encode local SIFT descriptors extracted from static images. The key tenet is to exploit, at the decoder side, the correlation between matching pairs of descriptors extracted, respectively, from the out-of-date and up-to-date image. Preliminary results show that a coding efficiency gain up to 1 bit/descriptor can be achieved in the case of ideal lossless coding. In the case of distributed source coding with LDPC codes, a practical average gain of 0.19 bit/descriptor is observed.