Network tap

Passive taps observe without interfering, for example by optically splitting the light in a fibre; active taps interact with the traffic, for instance by re-timing it or modifying headers to reduce covert channels ¹. RAND's verification framework includes mutually vetted devices that intercept data exchanged between accelerators and check it for discrepancies with declared uses ². In proposed designs such as network taps and certifiers, taps send out hashes of the traffic as cryptographic commitments instead of plaintext, so that the prover's declarations can later be checked against them ^{1 3}. Cankaya describes taps on the front-end links between a data centre and the outside world as the most viable, because those links carry little bandwidth ¹. The back-end fabric between accelerators has far higher bandwidth and strict latency requirements, and may call for random sampling rather than full capture ¹.