ORAM in Cloud Storage and Secure Processors

Intel SGX (Software Guard Extensions) provides hardware-isolated enclaves where code and data are encrypted and authenticated. However, the operating system can still observe which memory pages the enclave accesses by monitoring page table entries. This page-level access pattern can be exploited in side-channel attacks. A classic attack is the "controlled channel attack" by Xu, Cui, and Peinado (2015), which reconstructed RSA keys from SGX memory access patterns.

Beyond page-level access patterns, SGX is vulnerable to cache-timing side channels. An attacker sharing the processor can observe cache hits and misses caused by the enclave, inferring fine-grained (cache-line level) access patterns. These attacks work because the CPU cache is shared between the enclave and untrusted code. Mitigations include constant-time programming and ORAM to randomize memory access patterns.