Abstract: A method of scrambling a stream of data includes obtaining from the stream a succession of first sequences of blocks of data. The order of the blocks is reversed in each of the first sequences of blocks to form respective second sequences of blocks of data. The blocks in each second sequence of blocks are encrypted using a cipher in block chaining mode, initialised with a respective initialisation vector for each second sequence of blocks. For a succession of first sequences of blocks included in a unit of data within the stream, at least one initialisation vector for encrypting a second sequence of blocks formed from a first sequence of blocks in the unit is generated in dependence on at least one block in a preceding first sequence of blocks of the unit.

Abstract: A method is described of providing patches for software installed on a plurality of client systems. The method may include obtaining computer program code for inclusion in a patch, the code being arranged to co-operate with at least part of the software installed on a client system to perform a certain function after a patch has been applied in the client system. A first patch for application may be provided in at least one first client system with an instruction to update the actual patch level maintained in the client system to reflect a next level. The method may provide a second patch for at least one other of the client systems with an instruction to update the actual patch level maintained in the client system to reflect the next level. The code may be provided only in the first of the first and second patches.

Abstract: A method of external data storage in a system including a primary processing device, having a processor and a primary data storage unit, adapted to run application programs for processing active records in the processor and configured to store data belonging to active records in the primary data storage unit; and a secondary data storage system, accessible to the primary processing device, includes loading data belonging to an active record into the primary data storage unit and externalising the record by transferring at least a piece of data belonging to the record to the secondary data storage system for storage. The step of externalising a record includes the making of a call by an application program using data belonging to the record to an interface, arranged to transfer the piece of data to the secondary data storage system.