path-oram · research

Path ORAM

Path ORAM is a tree-based oblivious RAM protocol that reads and rewrites a full path while randomly remapping the accessed block.

Mechanism: A position map assigns each block a leaf. The block resides on that path or in the client's stash. After reading the old path, the client assigns a fresh random leaf and rewrites the old path, with randomized encryption and dummy padding. [1]

Memory: The stash holds blocks that cannot yet be placed. The position map is separate client state; recursion stores it in smaller ORAMs at additional access cost. The base protocol does not cover request timing leakage. [1]

Relations

related
Oblivious RAM, Authenticated encryption, Merkle tree

Citations

  1. Stefanov et al. Path ORAM: An Extremely Simple Oblivious RAM Protocol. JACM 65(4), 2018, sections 2-4 and 6.4. DOI 10.1145/3177872. (accessed 2026-11-12)

Further reading

  1. Hesela: What an encrypted access trace can reveal (accessed 2026-11-12)
Sources & caveats
  • The 2018 journal article extends the CCS 2013 publication (DOI 10.1145/2508859.2516660). No implementation, stash-failure experiment or cryptographic proof was reproduced.

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Hesela team. Path ORAM. Hesela. 2026-11-12. https://hesela.dev/terms/path-oram/