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Timing attacks

Level: 301 · deep dive

Stub — an outline, not a lesson. There is no runnable example behind this page yet, so nothing on it has been through the check that backs every other claim in this library. The bullets below are the questions the finished page has to answer.

One line: The channel nobody put in the threat model: how long the answer took.

The questions this page has to answer

  • Measure a naive byte-by-byte tag comparison and recover a tag from the timings.
  • Why is a branch on secret data the general form of this bug?
  • What does 'constant time' actually require — no branches, no table lookups indexed by a secret, no early return?
  • Why can you not write constant-time code reliably in a JIT'd or garbage-collected language?
  • Remote timing attacks are practical: what the network noise floor does and does not hide.

See also