A selective encryption encoder consistent with certain embodiments of the
invention has vertical and/or horizontal stripes encrypted. In one
embodiment, packets are examined in the digital video signal to identify
a specified packet type, the specified packet type being packets carrying
data representing a video slice wherein the video slice contains a larger
amount of data than a threshold (or a subsequent slice). The packets
identified as being of the specified packet type are encrypted using a
first encryption method to produce first encrypted packets. These first
encrypted packets are then used to replace the unencrypted packets in the
digital video signal to produce a partially encrypted video signal. The
packets of the specified type can also be multiple encrypted and replaced
in the data stream to produce a multiple encrypted video data stream.