Conditional Access to H.264/AVC Video with Drift Control

In this paper we address the problem of providing conditional access to video sequences, namely, to generate a low-quality video to be used as preview, which can be decoded at full quality if a decryption key is obtained. We propose and investigate the performance of two different techniques, based on smoothing and separate encoding in the compressed domain, and motion vector perturbation. We show that these techniques are able to provide conditional access to different quality levels of H.264/AVC video with very small rate overhead, and that their combination can provide different levels of security towards malicious attacks