Encrypted file system based on multi-image files

Abstract

The invention relates to an encrypted file system based on multi-image files. Each file in the encrypted file system is provided with a plurality of file images, i.e. a primary image file, a plurality of A image files, and a B image file; when one of the primary image files is opened or created by an untrusted process, the file opening or creating operation is redirected to one of the corresponding A image files, and the file opening or creating operations of different untrusted processes for the same primary image file are redirected to the different A image files; when one of the primary image files is opened or created by a trusted process, the file opening or creating operation is redirected to the corresponding B image file; the encrypted file system converts I / O operations for the A image files and the B image file of each file into operations for the corresponding original file, and automatically carries out file encryption and decryption processing during the operations. The encrypted file system provided by the invention avoids not only the mixing of cached data between the trusted processes and the untrusted processes, but also clear data leakage among the untrusted processes which might be caused by data storage and writing operations.

Description

technical field [0001] The invention belongs to the technical field of information security, in particular to an encrypted file system based on multi-image files. Background technique [0002] The transparent file encryption system can automatically realize the encryption and decryption of files without changing the user's usage habits, and is an important technical means to ensure data security. In transparent file encryption, program processes that perform file I / O operations on encrypted files are divided into trusted processes and untrusted processes. Trusted processes are allowed to obtain plaintext data of encrypted files, while untrusted processes are not allowed. In the current computer file system, in order to improve the efficiency of file I / O operations, most file I / O operations are cached, that is, the file system caches the data read and / or stored by the program process in the computer memory, and When different program processes perform file I / O operations on ...

AI Technical Summary

Problems solved by technology

File I / O with cache brings additional problems to transparent file encryption: when the trusted process and the untrusted process perform file I / O operations on an encrypted file at the same time, especially the alternate file data reading and writing operations , plaintext data and ciphertext data will alternately appear in the cache, which will cause the following problems: First, untrusted processes may read plaintext data, resulting in data leakage; second, program processes cannot process data correctly, such as trusted processes What is read is ciphertext data and cannot be processed normally

The problem with this solution is: first, it needs to frequently flush and clear the cache, resulting in the so-called violent flushing and clearing of the cache; second, when the trusted process and the untrusted process read and write data alternately, the It is very difficult to handle cache flushing and emptying

However, the scheme in the patent application 201510690514.9 also has the following problems: the file data stored and written by an untrusted process may be plaintext data (for example, a browser downloads and saves an unencrypted Word document), so when multiple untrusted processes File I / O operations on files being stored and written may cause data leakage

However, this solution is too troublesome, and it cannot completely solve the problem of data leakage. For example, when an untrusted process opens or creates a file in a memory-mapped manner and stores and writes plaintext data, the file driver of the dual-image encrypted file system or It may be too late when the additionally introduced file filter finds that the cached data in the memory is plaintext data, and the plaintext data in the cache may have been read by other untrusted processes (although the probability of this is very small)

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