Encrypted communication technology based on RTP protocol and national cryptographic SM4

With the continuous advancement of digital media, real-time streaming technology has found widespread applications. Various digital media platforms, such as video conferencing, online teaching, and live streaming, have emerged, with application scenarios constantly evolving. As technology progresses, the demand for security in real-time video transmission has grown significantly. To address the challenge of balancing security and low latency in real-time video transmission, this paper proposes an encrypted communication technology that integrates the RTP protocol with China's National Cryptographic SM4 algorithm. By leveraging H.264 hardware-accelerated encoding to reduce video data volume, a partial encryption strategy based on the payload of Network Abstraction Layer (NAL) units is implemented. The SM4 algorithm selectively encrypts core video content data, while lightweight obfuscation protects NAL headers, significantly reducing computational overhead for encryption and decryption while ensuring security. Combined with the streamlined encapsulation of the RTP protocol and UDP transmission mechanisms, a comprehensive low-latency transmission framework is established. Experimental results demonstrate that the proposed technology, integrated with Raspberry Pi hardware encoding optimizations and GStreamer pipelines, effectively resists known plaintext attacks, achieves end-to-end transmission latency below 100ms, and balances both security requirements and transmission efficiency for real-time video communication. The system employs attribute-based encryption for dynamic key management and distribution, providing an engineering-ready solution for secure real-time streaming media communication.