Malicious Node Identification in Coded Distributed Storage Systems under Pollution Attacks

In coding-based distributed storage systems (DSSs), a set of storage nodes (SNs) hold coded fragments of a data unit that collectively allow one to recover the original information. It is well known that data modification (a.k.a. pollution attack) is the Achilles’ heel of such coding systems; indeed, intentional modification of a single coded fragment has the potential to prevent the reconstruction of the original information because of error propagation induced by the decoding algorithm. The challenge we take in this work is to devise an algorithm to identify polluted coded fragments within the set encoding a data unit and to characterize its performance. To this end, we provide the following contributions: (i) We devise MIND (Malicious node IdeNtification in DSS), an algorithm that is general with respect to the encoding mechanism chosen for the DSS, it is able to cope with a heterogeneous allocation of coded fragments to SNs, and it is effective in successfully identifying polluted coded fragments in a low-redundancy scenario; (ii) We formally prove both MIND termination and correctness; (iii) We derive an accurate analytical characterization of MIND performance (hit probability and complexity); (iv) We develop a C++ prototype that implements MIND to validate the performance predictions of the analytical model. Finally, to show applicability of our work, we define performance and robustness metrics for an allocation of coded fragments to SNs and we apply the results of the analytical characterization of MIND performance to select coded fragments allocations yielding robustness to collusion as well as the highest probability to identify actual attackers.