Securely deleting invalid data from secondary storage is critical to protect users’ data privacy against unauthorized accesses. However, secure deletion is very costly for solid state drives (SSDs), which unlike hard disks do not support in-place update. When applied to SSDs, both erasure-based and cryptography-based secure deletion methods inevitably incur large amount of valid data migrations and/or block erasures, which not only introduce extra latency and energy consumption, but also harm SSD lifetime.
This paper proposes ErasuCrypto, a light-weight secure deletion framework with low block erasure and data migration overhead. ErasuCrypto integrates both erasurebased and encryption-based data deletion methods and flexibly selects the more cost-effective one to securely delete invalid data. We formulate a deletion cost minimization problem and give a greedy heuristic as the starting point. We further show that the problem can be reduced to a maximum-edge biclique finding problem, which can be effectively solved with existing heuristics. Experiments on real-world benchmarks show that ErasuCrypto can reduce the secure deletion cost of erasurebased scheme by 71% and the cost of cryptographybased scheme by 37%, while guaranteeing 100% security by deleting all the invalid data.