1. A method of secure demand paging (SDP) for portable telecommunication device having a processor, a secure internal memory, and an external DRAM comprising: configuring with configuration data indicating pages for confidentiality protection, and pages for integrity protection; multi-threading an SDP process and a non-secure process; executing the SDP process to swap between the external DRAM and the secure internal memory in response to page faults in the secure internal memory so that confidentiality processing is applied specifically to pages for which the configuration data indicates confidentiality protection, and integrity verification is applied specifically to pages for which the configuration data indicates integrity protection; and applying a process for determining when page replacement in the secure internal memory is necessary, and if so then applying a page replacement process for determination of priority for page replacement, that downgrades data pages in priority relative to code pages, downgrades recently loaded or accessed pages in priority relative to earlier loaded or accessed pages, and downgrades dirty pages in priority relative to clean pages in priority for page replacement.