hey, nice idea - but that's not how it works. there's no intrusion detection - an attacker increases the error rate, and by the error rate we can calculate the

hey, nice idea - but that's not how it works. there's no intrusion detection - an attacker increases the error rate, and by the error rate we can calculate the maximum probabilistic information an attacker plausibly might have. i say can, because that number is actually pretty uninteresting, since it isn't intrusion detection - we just now there's something causing the error rate to go up - doesn't have to be an attacker. a higher error rate in practice just means we gotta throw more bits away both during error correction and during privacy amplification - which is kinda like packetloss on a classical channel. at some point the error rate is too high for error correction with a positive yield (= more key lost in communication, than gained through said communication) - thus the scheme stops working. my personal favorite name is 'quantum key growing', because that's essentially what happens - you turn an initial shared secret (= random key) into a longer random key. (and while you're continually doing this, you're using up part of the previous key to secure communication as you go along)