Selective Encryption for Compressed Audio

Abstract

To achieve a real time secure transmission of audio over networks, a selective encryption method forcompressed audio is proposed in this paper. That is, instead of directly encrypting the entire audio, theproposed method only encrypts a small important part extracted from that audio, and the encrypted part isused to protect the contents of the remaining audio. By considering a standard MPEG 1 Layer IIIbit-stream, some parameters can be extracted and used as the important parts. Thus, in this paper, weconsider four parameters extracted from the side information of a MP3 bit-stream, namely, main_data_begin,scfsi, part2_3_length and table_select, for the selective encryption. Their performances, when implementedin an encryption scheme, in terms of quality of the encrypted audio and complexity of the encryptionprocess, are evaluated and compared with ordinary encryption methods. The results show that, by using themain_data_begin as an important part, the processing time required in the encryption process can bereduced by 99.71 %, on average, while maintaining the security level of the encrypted audio. Our approachenables a real time encryption for MP3 music delivery via the Internet. Furthermore, it can be applied toother audio compression standards.