Encrypting VoLTE Communication via Baseband Firmware Extension

VoLTE is a technology carried on 4G network by RTP, and realizes the unification of data and voice communication. At the same time, it also faces the vulnerability of wireless communication. This paper proposes a HOOK-based method to modify the mobile phone baseband to implement end-to-end encrypted VoLTE calls. The experiment first builds a framework with assembly code, which can hook the process functions for sending and receiving packet, in order to capture the RTP data packet and inject the encryption and decryption patch function. Then through the analysis of the data packet, the key agreement and extension using the packet header is completed by C language. The automatic voice data encryption with AES 256 algorithm is realized through the library functions in the baseband. In conclusion, the experiment implements a one-time pad encryption mechanism to ensure VoLTE communication security, so that even if a third party intercepts the data packet, the information cannot be leaked.