A method and system enables network intermediaries such as proxies to transcode multimedia data without violating end-to-end security guarantees. In one embodiment, a content provider decomposes a data stream into a plurality of components, each of which are independently encrypted. In a preferred embodiment, an intermediary or proxy performs transcoding of the components by prioritizing and dropping predetermined components, in accordance with unencrypted clear-text metadata associated with each component, without the need for decrypting the components. Clear-text metadata preferably provides a semantic understanding of the absolute or relative importance/priority of the components with respect to each other, thereby facilitating the transcoding process. The destination/client device can subsequently decrypt the components transmitted by the transcoding proxy and reassemble them into a representation of the original data content.