Research On General Encryption Transmission Method Based On Android

With the rapid development of mobile Internet,mobile terminals are also becoming more popular.Mobile applications infiltrate users' social life,shopping,news,entertainment and so on.However,when data is transmitted on the Internet,it is most likely to be subject to malicious third-party monitoring,interception or even tampering.In particular,transmitting payment information and private data will cause incalculable losses once it is revealed.Therefore,the security of information transmission in mobile terminals needs to be solved.This paper aims at the security problem of mobile terminals based on Android system in the information transmission,and studies the general encryption method that is transparent to high-level applications,and gives implementation.This design compiles the kernel source code of Android system,and writes a kernel module that can be dynamically loaded into the Linux kernel layer of Android system.Through the Linux kernel subsystem Netfilter,TCP/UDP data packets are automatically encrypted and decrypted by the AES algorithm provided by the kernel or XOR shift algorithm,when entering and leaving the network stack for high-level applications.After modifying the data packet,it is necessary to recalculate and set the relevant length variable and checksum,and continue the processing of the protocol stack.It also supports automatic key agreement at the kernel level.When sending a specified number of encrypted packets,a key negotiation packet will be constructed and sent.This kind of dynamic loading method changes the key transparently and automatically to users,which can effectively increase the security of communication.This paper gives the architecture design,and designs message transmission,records saving,records viewing,key agreement module.Message transmission module based on TCP or UDP is implemented;Records saving module allows user-defined passwords to encrypt records and save in the file,using the combination of AES encryption and Base64 encoding.The password is stored in the Shared Preference,using Base64 encoding and MD5 calculation digest;Record viewing module performs the Base64 encoding and MD5 digest calculation on the password entered by the user.The obtained result will be compared with the values stored in the Shared Preference.If they match,the decrypted communication records can be viewed.The use of the MD5 algorithm ensures the reversibility of password security;Key agreement module allows users to manually perform key agreement based on the discrete logarithmic DH algorithm to generate the key.Finally,save the key in a file.The experiment shows that the general encryption method for the information transmission based on Android system proposed in this paper is feasible.When the kernel module is loaded,data is transmitted in ciphertext on the network,and both applications display plaintext.After the module is unloaded,the data is transmitted in clear text on the network.This method is transparent to Android users and applications,and easy to load and unload.It's no need to change the code of third-party applications,so the method has strong versatility and usability.