User-Level Secure Deletion on Log-Structured File Systems
The authors address the problem of secure data deletion on log-structured le systems. They focus on the YAFFS le system, used on Android Smartphones, and on the Flash Translation Layer (FTL), used in SD cards and USB memory sticks. They show that neither of these systems provides temporal data deletion guarantees and that deleted data remains indefinitely on these systems if the storage medium is not used after the data is marked for deletion. Moreover, the time that data remains on log-structured file systems increase with the storage medium's size. They propose two user-level solutions that achieve secure deletion: purging, which ensures that all data is deleted, and ballooning, which reduces the expected deletion latency.