In order to service heterogenous, variable bandwidth networks, low complexity transcoding architectures have been developed to allow modification of video bitrate. SVC, the scalable extension to H.264, was also developed for this purpose. When encrypted video is transmitted, it cannot be modified prior to decryption. Any decryption carried out at a transcoder would use security weaknesses in the network. In the above context, there is a need to develop transparent encryption techniques that allow bitrate reduction without decryption. For SVC bitstreams, an architecture called SVE is presented in this thesis to allow the full range of scalabilities to be supported without compromising quality or security. This approach is shown to outperform all existing techniques presented in the literature and shows significant potential for commercial deployment.