Design And Implementation Of Double File System Based On Android Platform

Android operating system is a kind of operating system which has the largest market share of smart mobile phone in the world. Compared to other mobile operating system Android has many advantages, such as its open source, customizable property and playability, so it has a large number of users. With the deepening of people's dependence on smart phones, more and more secret file data is stored in the smart phone, in this trend, personal privacy security has become the focus of attention.But the privacy data storage and protection mechanisms of the Android operating system itself are scarce and far from satisfying people's data security needs. In this regard, the major mobile phone manufacturers have provided the appropriate security measures in their respective devices, so that the users' privacy has a certain degree of protection. However, in some special cases, the phone can not play a role in providing security measures, for example, a user or s reporter is held hostage and in a dangerous situation with a mobile phone forensics, some people force to check the user or reporter's mobile phone. At this point, the original operating system protection measures will be invalid.In order to solve the problem of data secure storage for Android users,this paper proposes a double file system model based on Android platform, which combines file system customization and System Service customization to design and implement double file system and transparent encryption service. Double file system is implemented in the Android kernel layer, this paper establishes a new hidden file system, and modifies Android Ext4 file system source code to solve the problem of double file system data write confliction, so that the visible file system Data block allocation can avoid the hidden file system when writing, the double file system model hides sprivacy file data through the realization of hidden file system, and dynamic mount function further optimizes the data hiding effecttion. Transparent encryption services are mainly implemented in the Android application framework layer, this paper add System Service to accomplish the development of the transparent encryption service, the transparent encryption services uses AES 128 encryption algorithm to ensure high encryption strength, the transparent encryption service also provides a SDK development interface to the application layer.This paper builds the Android CM13 source development and compiling environment in ubuntu environment, and compiles the system source code of customized double file system and transparent encryption service. it generates ROM successfully, this paper installs the ROM to the test mobile phone, then tests and validates the performance of the double file system.this paper develops an App for the transparent encryption service, then tests and validates the encryption effect. the result proves that the model is correct and reliabile. In the end of this paper, this paper makes a comprehensive summary of the design and implementation of the model according to the function of the model and the actual test results, and puts forward the deficiency of the model and the direction of improvement.