International Association
for Cryptologic Research

We propose \\emph{RAW Path ORAM}, an ORAM construction that improves the state of the art Path ORAM in several ways.

First, RAW Path ORAM reduces the amount of encryption operations by $4\\times$ compared with Path ORAM.

Second, RAW Path ORAM enables a much more efficient and simpler integrity verification scheme.

Third, RAW Path ORAM dramatically simplifies the theoretical analysis on client storage requirement (stash size).

We build RAW Path ORAM in hardware and name it \\emph{Tiny ORAM}.

Tiny ORAM is the first hardware ORAM design that efficiently supports small client storage, arbitrary block sizes (e.g., 64~Bytes to 4096~Bytes) and integrity verification.

Block size flexibility allows Tiny ORAM to greatly reduce the worst-case access latency for ORAM running programs with erratic data locality.

To reduce the performance overhead that comes with small client storage, we add \\emph{Unified ORAM} scheme that further decreases ORAM access latency by up to 39\\% on real workloads.

We demonstrate a complete working prototype on a stock FPGA board.

Tiny ORAM requires $5\\%/15\\%$ of the FPGA logic/memory (including encryption and integrity verification)

and can complete an ORAM access for a 64 Byte block in $1.25-4.75\\mu s$.