◄ Wiki / Crypto
timing leak / side channel
When how long an operation takes secretly reveals the private data it worked on.
If a computation's duration depends on secret values — a key, a comparison result — an attacker who measures timing can infer those secrets without ever seeing them directly; this is a side channel. Constant-time code avoids it by taking the same time regardless of the data. Some operations, like verifying a signature with only public inputs, have no secret to leak and can safely be non-constant-time.
See also
- table-free AESAn AES encryption implementation that avoids memory lookup tables so its timing can't leak the secret key.
- test vectorsOfficial known input-and-expected-output pairs used to prove a crypto implementation is correct.
- to-be-signed (TBS) bytesThe exact bytes of a certificate that a digital signature actually covers.