Research And Implement Of Secure File System

With the rapid development of the electronic information technology, the electronic file is used extensively. The security of the electronic information becomes focus in the field of information security. The secure storage of e-file is the precondition of ensuring information security, which is generally realized by encryption. There are two methods to cryptographic storage: one is encrypting the whole disk space through setting up a virtual disk; the other is encrypting the individual file separately.This paper describes the design and realization of two methods of file encryption. At first, this paper briefly introduces the foundational knowledge of cryptography. Then emphasizes the principle and implementation of two file encryption systems (virtual disk encryption system and direct file encryption system). The ultimate of the virtual disk encryption system is as follows: partition some spaces off from the hard disk, set up the volume file, and mount it as a virtual disk. The hard disk driver accesses e-files on the virtual disk. A special code/decode procedure in the virtual disk driver is used to encrypt files before writing and decrypt files after reading. Thus the secure storage of the information is realized. The direct file encryption system encrypts the individual file, which decrypts file before using, encrypts file before saving. And signature/authentication is also realized.The virtual disk encryption system is realized based on PGPdisk including three major modules: user interface module, encryption module and driver module. This paper analyses the principles and designs of these three modules in detail. With the concrete functions, introduces the produce of random number, the accessing control strategy, the realization of encrpytion algorithm, driver and file encryption/decryption. The direct file encryption system is realized based on OPENSSL including three major modules: user interface module, interface module, base encryption module. This paper introduces the demand analysis and function design in detail, gives the source codes of relevant interface functions and base algorithm.