Privacy-Protection SSD with Precision ECC and Crush Techniques for 15.5× Improved Data-Lifetime Control

The privacy-protection solid-state storage (PP-SSS) system is a proposal for Internet-data's "right to be forgotten", in which data-lifetimes are specified without file-system overhead. In NAND flash memory, the data-lifetimes are controlled by intentionally injecting errors into the data during write, to accelerate retention failure. However, the previously reported PP-SSS [1] has 2 issues, wide variation of data-lifetime and limited effectiveness for uncompressed data. In this work, based on 1Xnm TLC NAND flash measurement, 2 improvement techniques are demonstrated. Precision ECC increases the ECC codeword length and crush judges when the data expires and converts it to black/ irrecoverable data. When precision ECC and crush are applied to conventional PP-SSS, data-lifetime variation decreases by 15.5×, from 31 days to 2 days, and both compressed and uncompressed data can be protected.