A system for streaming encrypted conditional access (CA) data, such as control
words, from a primary or master conditional access provider (CAP) to one or more
secondary CAPS. The primary CAP encrypts content (program data) that is to be access-controlled,
such as a television program, according to the associated CA data. A first group
of user terminals is compatible with the CA data of the primary CAP. The CA data
is then provided to the secondary CAPs to provide corresponding CA data for the
content in the secondary CAPs' associated formats for compatibility with other
groups of terminals. The invention can be used in any packet-based distribution
system, including a broadband television network headend, and avoids the need for
the secondary CAPs to request the control words on an as-needed basis. Moreover,
the CA data for a current crypto-period and a number of future crypto-periods are
provided in a "sliding window" to allow the secondary CAP to begin preparing its
CA data in advance. Moreover, the CA data can be provided to the secondary CAPs
on a real-time basis, or well beforehand when the content is pre-encrypted and
stored, e.g., at a file server.
