[tor-dev] Proposal Waterfilling

Aaron Johnson aaron.m.johnson at nrl.navy.mil
Wed Mar 7 13:54:36 UTC 2018

>> 1) The cost of IPs vs. bandwidth is definitely a function of market offers. Your $500/Gbps/month seems quite expensive compared to what can be found on OVH (which is hosting a large number of relays): they ask ~3 euros/IP/month, including unlimited 100 Mbps traffic. If we assume that wgg = 2/3 and a water level at 10Mbps, this means that, if you want to have 1Gbps of guard bandwidth,
>> - the current Tor mechanisms would cost you 3 * 10 * 3/2 = 45 euros/month
>> - the waterfilling mechanism would cost you 3 * 100 = 300 euros/month
> The question of what the cheapest attack is can indeed be estimated by looking at market prices for the required resources. Your cost estimate of 3.72 USD/Gbps/month for bandwidth seems off by two orders of magnitude.

I see that I misread your cost calculation, and that you estimated $37.20/Gbps/month instead of $3.72/Gbps/month. This still seems low by an order of magnitude. Thus, my argument stands: waterfilling would appear to decrease the cost to an adversary of getting guard probability compared to Tor’s current weighting scheme.


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