Distributed Secure Storage: Rate-Privacy Trade-Off and XOR-Based Coding Scheme
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We consider the problem of storing data in a distributed manner over T servers. We require the data (i) to be recoverable from the T servers, and (ii) to remain private from any T-1 colluding servers, where privacy is quantified in terms of mutual information between the data and all the information available at the T-1 colluding servers. For this model, we determine (i) the fundamental trade-off between storage size and the level of desired privacy, (ii) the optimal amount of local randomness necessary at the encoder, and (iii) an explicit low-complexity coding scheme that solely relies on XOR operations and that asymptotically (with the data size) matches the fundamental limits found.
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