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 both packets
carrying intra-coded data representing a pattern of horizontal stripes
across an image and packets carrying intra-coded data representing a
pattern of vertical stripes across an image. 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.