Potential HS guard discovery using bw stats
Bandwidth stats are included in extra-info descriptor for 15 minute intervals. This allows an attacker to do a guard discovery attack, by modulating traffic he sends to an HS every 15 minutes and then checking all the relay stats to see which one matches the modulation.
It was mentioned by Aaron here: https://lists.torproject.org/pipermail/tor-dev/2014-November/007829.html
It's clear we need to increase the reporting period, so that the modulation is hidden inside the noise of unrelated traffic. We should probably increase the reporting period to every 6-12 hours or a full day. Is something using the 15-minute interval measurements that would break if we decreased the reporting frequency?
Also, is this a sufficient fix or do we need to do more?