## A channel cannot transmit reliably at rates above capacity

## Corollary: The capacity of a protocol is the (tight) upper bound on the rate of a reliable DRQS attack.

## While the protocol is not perfect, there is a cost to exploiting its non-perfectness

## Bound also holds for: n → 0 ; adaptive, non-deterministic; also many other protocols

## i.e. n → 0 lim k/n C