An audio encryption technique based on LFSR based alternating step generator

In this paper, a novel method of encrypting the encoded audio data based on LFSR based key stream generators is presented. The alternating step generator (ASG) is selected as keystream generator used for this application. Since the ASG is vulnerable to improved linear consistency attack, it is proposed to incorporate some nonlinearity with the stop/go LFSRs of the ASG so that the modified ASG can withstand the same. In the proposed approach, the selected bits of each frame of the encoded audio data is encrypted with the keystream generated by the modified ASG. In order to overcome known plaintext attack, it is proposed to use different keystreams for different frames of the audio data. The long keystream generated from the modified ASG is divided into smaller keystreams so that it can be used as the different keystreams for different frames of audio data. The proposed encryption approach can be applied to any audio coding system, which maintains the standard compatibility. The number of encrypted bits control the degree of degradation of the audio quality. The performance of proposed encryption method is verified with MP3 coded audio data and is proved that it can provide better security than the existing ones with very less system complexity.