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Side-channel attacks

These attacks don’t break the enclave directly, they infer secrets by watching its behavior, such as timing differences or physical emissions.

SGX‑Step (Interrupt‑driven single‑stepping attack)​

SGX‑Step is an open‑source framework that lets an untrusted OS raise high‑frequency APIC timer interrupts, effectively single‑stepping an enclave one instruction at a time, debugger-like. By precisely measuring where each Asynchronous Enclave Exit (AEX) occurs, an attacker can: reconstruct fine‑grained control‑flow, defeat in‑enclave ASLR, mount data‑oriented or branch‑shadowing attacks that extract secrets such as key‑dependent branches and memory indices.

Mitigation:

  • Detect or rate‑limit frequent AEX events inside the enclave and abort if a threshold is exceeded.
  • Adopt constant‑time, data‑oblivious code paths so that observing instruction‑level control‑flow leaks no secret‑dependent behaviour.
  • Long‑term: hardware extensions such as AEX‑Notify let trusted enclave code run immediately after every interrupt, blocking precise single‑stepping in commodity CPUs.

CacheZoom (Timing-based attack)​

By carefully measuring how long certain memory operations took, attackers reconstructed secret access patterns in SGX.

Mitigation: Developers can use constant-time algorithms and memory obfuscation techniques like ORAM to reduce timing leaks.

Power & EM analysis​

Observing power draw or electromagnetic signals during enclave execution can reveal cryptographic keys or sensitive data.

Mitigation: Injecting noise, isolating sensitive workloads, and rotating keys regularly can make these attacks infeasible in practice.