Research On File Encryption System For Android Devices

The mobile device stores a lot of pictures,videos and other important data,such as on-site law enforcement data on police terminals.If the data on the mobile device is leaked,it may cause great loss to the user,and even trigger hot public opinions.Therefore,it is very important to ensure the data security on mobile devices.The choice of data encryption strategy for mobile devices must consider the balance between computing load and security due to the limitations of mobile device performance.Compared with traditional encryption technology,the security of content associated key technology does not depend completely on computational complexity,and is more suitable for file encryption and decryption processing in mobile devices.An encryption algorithm for MP4 files is designed based on content association key technology.Firstly the algorithm analyzes MP4 file format to locate video data frames in the file and determine the key extraction location in units of frames(or a set of frames)using the improved PWLCM chaotic map.It is determined to extract the corresponding data of key frames and non-key frames in the file through research in order to achieve better encryption effect,and then synthesize the key for the entire file.At the same time,the encryption effect of MP4 file is tested from the aspects of encrypted video image effect and PSNR value analysis,and the validity of the algorithm was verified.In addition,the algorithm can be applied to the encryption of other types of files such as pictures and documents after appropriate modification.Based on the Android platform,a file encryption system is designed and implemented using the above encryption algorithm to perform encryption and decryption processing on various types of files in Android devices.In the file encryption system,the system encrypts the file by calling the corresponding encryption algorithm according to the file type.After the encryption is completed,the extracted key is uploaded to the key server and the ciphertext is retained in the mobile device(or stored in the cloud)to ensure the security of the files in the mobile device.When decrypting,after the ciphertext is selected,the system will connect to the key server to obtain the key and automatically decrypt the ciphertext,and then the user can obtain the original file.The system also supports key sharing.After ciphertexts are shared between users,when sharers need to decrypt the system will initiate a key authorization application to the key master and choose whether to provide the key to the sharer according to the authorization result,so as to achieve file security sharing.The result shows that the file encryption system realizes the designed function and can enhance the security of file storage and sharing in mobile devices.In addition,experiments on the performance of multi-threaded concurrent processing of MP4 format files show that multi-threaded concurrency can improve the speed of file encryption and decryption.