The Design & Realization Of Linux-based Encrypt NAND Flash Filesystem

NAND Flash is having a important role in the nonvolatile storage architectures because its great characteristics of big storage capacity, low price, antishock and low power consumption, it have be largely used into Consumer Electronics Device, aviation and space equipment. Because of NAND Flash have the special storage charater which is different from the disk, we need to apply the special solutions to manage the date store in the storage medium. At present, we have two main solutions include FTL+disk filesystem and Flash filesystem. Flash filesystem is widely used in embedded application, it generally choose the log-structured design, support shutdown management and crash recovery.As NAND Flash is used widely in embedded applications, we have to pay more attention to security of date that store in Flash storage medium. Because the embedded equipment generally have the characteristics as small, portable and disposing in public place, if the equipment is lost or stolen, the date in the storage medium will lost and be acquired illegally, which may damage the benefit of owners, even threating the country information security. Encryption file system is one of the major ways to resist the physics attack. It can encrypt the date with file granularity, have strong ability in anti-decrypt and will be transparent to user which making it easy to use. So, it will have reality value and significance to design and realization an ecryption filesystem aim at NAND Flash.At first step, this paper analysis the NAND Flash's special storage charaters and the filesystem architecture that applied in Linux kemel.Then I do the research about the ecryption filesystem as EFS in windows, CFS and eCryptfs and work over their program aechitecture and ecrypt mechanism. I analysis the YAFFS2's source code intently and make out the procedure of YAFFS2's initialize mount, the way to read/write data from/into NAND Flash, the process that create the Object structure and garbage collection mechanism. After that, I design the overall architecture of NFEFS. Finish the key management method, implement the detail procedure of encrypt/decrypt the file date and ObjectHeader to protect the plaint date and file structure, realiztion the support to different Linux kernel edition. At last, design the plan to test the NFEFS's I/O performance, make the analysis to the result.