Schemes for Privacy Data Destruction in a NAND Flash Memory

Abstract

We propose schemes for efficiently destroying privacy data in a NAND flash memory. Generally, even if privacy data is erased from NAND flash memories, there is a high probability that the data will remain in an invalid block. This is a management problem arising from characteristics of a program operation and an erase operation of NAND flash memories. When updating pages or performing a garbage collection, there is a problem that valid data remains in at least one unmapped memory block. Is it possible to impose an obligation to delete privacy data from an existing NAND flash memory? This paper is the answer to this question. We propose a partial overwriting scheme, an SLC programming scheme, and a deletion duty pulse application scheme for invalid pages to effectively address privacy data destruction issues caused by the remaining data. Such privacy data destruction schemes basically utilize at least one state in which data can be written to programmed cells based on a multi-level cell program operation. Our privacy data destruction schemes have advantages in terms of block management as compared with conventional erasing schemes, and are significantly economical in terms of time and cost. The proposed privacy data destruction schemes may be easily applied to many storage devices and data centers using a NAND flash memory.