STEP-archival: Storage Integrity and Anti-Tampering using Data Entanglement

We present STEP-archives, a model for censorship-resistant storage systems where an attacker cannot censor or tamper with data without causing a large amount of obvious collateral damage. MDS erasure codes are used to entangle unrelated data blocks, in addition to providing redundancy against storage failures. We show a tradeoff for the attacker between attack complexity, irrecoverability, and collateral damage. We also show that the system can efficiently recover from attacks with imperfect irrecoverability, making the problem asymmetric between attackers and defenders. Finally, we present sample heuristic attack algorithms that are efficient and irrecoverable (but not collateral-damage-optimal), and demonstrate how some strategies and parameter choices allow to resist these sample attacks.