NASA: NVM-Assisted Secure Deletion for Flash Memory

Secure deletion in flash-based storage is crucial for data security. However, existing secure deletion schemes for flash memory suffer from performance degradation and reliability issues and cannot provide secure deletion guarantees. Although emerging nonvolatile memory (NVM) allows in-place updates and provides high performance, it is unable to fully replace flash memory and, thus, cannot solve the secure deletion problem. In this article, we propose NVM-assisted secure deletion scheme for flash memory (NASA), a stale-free storage system that combines NVM and flash memory to provide immediate secure deletion without significant performance degradation in SSDs. NASA uses block erasure to provide secure deletion guarantees for flash memory and exploits NVM to conceal time-consuming erasure operations. We demonstrate that unless the unique characteristics of NVM are considered, schemes that merely implement existing approaches to secure deletion will end up with stale data replicas within their storage media. Moreover, we evaluate NASA with different real-world workloads and demonstrate that NASA increases the average latency by 0.01% compared to LRU and decreases 2.1% average latency over the FIFO caching policy. NASA is a novel storage system that provides strong secure deletion guarantees with high performance.