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NAND flash memory-based SSDs have been widely adopted. The scaling of SSD has evolved from plannar (2D) to 3D stacking. For reliability and other reasons, the technology node in 3D NAND SSD is larger than in 2D, but data density can be increased via increasing bit-per-cell. In this work, we develop a novel reprogramming scheme for TLCs in 3D NAND SSD, such that a cell can be programmed and reprogrammed several times before it is erased. Such reprogramming can improve the endurance of a cell and the speed of programming, and increase the amount of bits written in a cell per program/erase cycle, i.e., effective capacity. Our work is the first to perform a real 3D NAND SSD test to validate the feasibility of the reprogram operation. From the collected data, we derive the restrictions of performing reprogramming due to reliability challenges. Furthermore, a reprogrammable SSD (ReSSD) is designed to structure reprogram operations. ReSSD is evaluated in a case study in RAID 5 system (RSS-RAID). Experimental results show that RSS-RAID can improve the endurance by 35.7%, boost write performance by 15.9%, and increase effective capacity by 7.71%, with negligible overhead compared with conventional 3D SSD-based RAID 5 system.

Hierarchical key assignment scheme is an efficient cryptographic method for hierarchical access control, in which the encryption keys of lower classes can be derived by the higher classes. Such a property is an effective way to ensure the access control security of Internet of Things data markets. However, many researchers on this field cannot avoid potential single point of failure in key distribution, and some key assignment schemes are insecure against collusive attack or sibling attack or collaborative attack. In this paper, we propose a hierarchical key assignment scheme based on multilinear map to solve the multigroup access control in Internet of Things data markets. Compared with previous hierarchical key assignment schemes, our scheme can avoid potential single point of failure in key distribution. Also the central authority of our scheme (corresponding to the data owner in IoT data markets) does not need to assign the corresponding encryption keys to each user directly, and users in each class can obtain the encryption key via only a one-round key agreement protocol. We then show that our scheme satisfies the security of key indistinguishability under decisional multilinear Diffie-Hellman assumption. Finally, comparisons show the efficiency of our scheme and indicates that our proposed scheme can not only resist the potential attacks, but also guarantee the forward and backward security.

The reliability of solid-state drives (SSDs) has become increasingly important as SSDs are now widely applied in data centers. Retention error is a major source of impact on the reliability of SSDs. Even though the common practice in understanding the retention errors of an SSD is done by high-temperature baking processes, their characterization accuracy is not yet rigidly reviewed. In this paper, we first present how the common retention acceleration method goes wrong. Through a one-year study of 3D flash error behaviors, we found that the retention errors through baking with high temperatures have very different characteristics from the real long-retention errors. These differences come from the inherent structure and the materials of 3D NAND flash. Several findings regarding the retention errors characterized through baking are presented, followed by the analysis of the error behaviors. Finally, the retention errors of one year on 3D flash memory are provided with real data.

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Abstract. According to the characteristics and state of Chinese art design teaching, we integrated modern educational technology in the current teaching places with a set of electronic double board, teacher-student interaction system and cloud resource platform system. In order to achieve better teacher-student interaction in the future with the premise of Grand Designs, systematic integration and ecological civilization, we formed a special advanced teaching system for art and design disciplines. The system not only provides a reference for the development of the current art design teaching mode, but also can be verified by practice in the continuous evolution of the teaching system.

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