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Keystone is a trusted execution environment, based on RISC-V architecture. Itdivides the memory into a secure Keystone private memory and an unsecurenon-Keystone memory, and allows code that lies inside the Keystone privatememory to execute securely. Simple demand paging in Keystone ends up leakingsensitive access patterns of Keystone application to the Operating System(OS),that is assumed to be malicious. This is because, to access the unsecurenon-Keystone memory, Keystone needs support of the OS. To mitigate this,Keystone needs to implement oblivious demand paging while obfuscating its pageaccess patterns by using Oblivious RAM(ORAM) techniques. This causessubstantial slowdown in the application execution.  In this paper, we bridge the performance gap between application executiontime with unsecure and secure demand paging in Keystone by using Deterministic,stash free, Write only ORAM (DetWoORAM) for oblivious demand paging. We alsoshow why DetWoORAM, that is a write-only ORAM, is sufficient for obliviousdemand paging. DetWoORAM logically partitions the memory into a main area and aholding area. The actual pages are stored in main area. We propose twoenhancements over DetWoORAM that improves the application execution slowdown.The first enhancement, which we call the Eager DetWoORAM, involves pagepreloading that exploits the deterministic access pattern of DetWoORAM, andtries to hide the ORAM latency. The second enhancement, which we call theParallel DetWoORAM, involves spawning multiple threads and each thread performsa part of the DetWoORAM memory access algorithm. Compared to DetWoORAM thatshows slowdown of [1.4x, 2x, and 3.24x], Eager DetWoORAM and Parallel DetWoORAMprovide slowdown of [1.2x, 1.8x, and 3.2x] and [1.1x, 1.1x, and 1.4x], for k=3, 7, and 15, respectively.

Introducing Fast and Secure Deterministic Stash Free Write Only Oblivious RAMs for Demand Paging in Keystone