— an application for assuring the authenticity of audio-video information is developed. The application is implemented in Java by using Java Media Framework to send audio and video information over RTP (Real-time Transport Protocol). In order to guarantee that information is not altered during transmission over public networks by malicious adversaries some cryptographic functions and protocols are used for achieving information authenticity. More concrete, a cryptographic protocol which uses Message Authentication Codes and elements of a one-way chain as keys is implemented. The solution proves to be efficient and the computational costs are kept to a minimum.