Visible to the public Biblio

Filters: Author is Chang, Yuan-Hao  [Clear All Filters]
Lin, Ping-Hsien, Chang, Yu-Ming, Li, Yung-Chun, Wang, Wei-Chen, Ho, Chien-Chung, Chang, Yuan-Hao.  2018.  Achieving Fast Sanitization with Zero Live Data Copy for MLC Flash Memory. 2018 IEEE/ACM International Conference on Computer-Aided Design (ICCAD). :1–8.
As data security has become the major concern in modern storage systems with low-cost multi-level-cell (MLC) flash memories, it is not trivial to realize data sanitization in such a system. Even though some existing works employ the encryption or the built-in erase to achieve this requirement, they still suffer the risk of being deciphered or the issue of performance degradation. In contrast to the existing work, a fast sanitization scheme is proposed to provide the highest degree of security for data sanitization; that is, every old version of data could be immediately sanitized with zero live-data-copy overhead once the new version of data is created/written. In particular, this scheme further considers the reliability issue of MLC flash memories; the proposed scheme includes a one-shot sanitization design to minimize the disturbance during data sanitization. The feasibility and the capability of the proposed scheme were evaluated through extensive experiments based on real flash chips. The results demonstrate that this scheme can achieve the data sanitization with zero live-data-copy, where performance overhead is less than 1%.
Chen, Shuo-Han, Yang, Ming-Chang, Chang, Yuan-Hao, Wu, Chun-Feng.  2019.  Enabling File-Oriented Fast Secure Deletion on Shingled Magnetic Recording Drives. 2019 56th ACM/IEEE Design Automation Conference (DAC). :1—6.

Existing secure deletion approaches are inefficient in erasing data permanently because file systems have no knowledge of the data layout on the storage device, nor is the storage device aware of file information within the file systems. This inefficiency is exaggerated on the emerging shingled magnetic recording (SMR) drive due to its inherent sequential-write constraint. On SMR drives, secure deletion requests may lead to serious write amplification and performance degradation if the data layout is not properly configured. Such observation motivates us to propose a file-oriented fast secure deletion (FFSD) strategy to alleviate the negative impacts of SMR drives' sequential-write constraint and improve the efficiency of secure deletion operations on SMR drives. A series of experiments was conducted to demonstrate the capability of the proposed strategy on improving the efficiency of secure deletion on SMR drives.

Wang, Wei-Chen, Lin, Ping-Hsien, Li, Yung-Chun, Ho, Chien-Chung, Chang, Yu-Ming, Chang, Yuan-Hao.  2019.  Toward Instantaneous Sanitization through Disturbance-induced Errors and Recycling Programming over 3D Flash Memory. 2019 IEEE/ACM International Conference on Computer-Aided Design (ICCAD). :1—8.

As data security has become one of the most crucial issues in modern storage system/application designs, the data sanitization techniques are regarded as the promising solution on 3D NAND flash-memory-based devices. Many excellent works had been proposed to exploit the in-place reprogramming, erasure and encryption techniques to achieve and implement the sanitization functionalities. However, existing sanitization approaches could lead to performance, disturbance overheads or even deciphered issues. Different from existing works, this work aims at exploring an instantaneous data sanitization scheme by taking advantage of programming disturbance properties. Our proposed design can not only achieve the instantaneous data sanitization by exploiting programming disturbance and error correction code properly, but also enhance the performance with the recycling programming design. The feasibility and capability of our proposed design are evaluated by a series of experiments on 3D NAND flash memory chips, for which we have very encouraging results. The experiment results show that the proposed design could achieve the instantaneous data sanitization with low overhead; besides, it improves the average response time and reduces the number of block erase count by up to 86.8% and 88.8%, respectively.

Chen, Ping-Xiang, Chen, Shuo-Han, Chang, Yuan-Hao, Liang, Yu-Pei, Shih, Wei-Kuan.  2021.  Facilitating the Efficiency of Secure File Data and Metadata Deletion on SMR-based Ext4 File System. 2021 26th Asia and South Pacific Design Automation Conference (ASP-DAC). :728–733.
The efficiency of secure deletion is highly dependent on the data layout of underlying storage devices. In particular, owing to the sequential-write constraint of the emerging Shingled Magnetic Recording (SMR) technology, an improper data layout could lead to serious write amplification and hinder the performance of secure deletion. The performance degradation of secure deletion on SMR drives is further aggravated with the need to securely erase the file system metadata of deleted files due to the small-size nature of file system metadata. Such an observation motivates us to propose a secure-deletion and SMR-aware space allocation (SSSA) strategy to facilitate the process of securely erasing both the deleted files and their metadata simultaneously. The proposed strategy is integrated within the widely-used extended file system 4 (ext4) and is evaluated through a series of experiments to demonstrate the effectiveness of the proposed strategy. The evaluation results show that the proposed strategy can reduce the secure deletion latency by 91.3% on average when compared with naive SMR-based ext4 file system.