A few comments on the comments: This is not a case of Jevons paradox and perhaps the best way to understand this is to consider what would make it apply. If Tor were to change its protocol and use more efficient cryptography to do simple, repetitive tasks like circuit building (maybe use Pairing-based crypto, as suggested at PET), the speed to process a user’s data would hypothetically increase. In other words, Tor’s efficiency is being increased.

W.S. Javons (who btw came an inch away from inventing RSA a hundred years before) originally would have predicted that this would result in less demand for Tor. If I can do all my web browsing in a fraction of the time it used to take, then I will be using Tor less. However Javons soon realized that, as Steven points out in his article, that this assumes the user base does not change. First I might surf longer with Tor since its faster. And second, new users how would have considered it too slow before will start using it. And so increasing the efficiency of Tor has the exact same effect as giving it more bandwidth (and perhaps an equally articulated fallacy in the PET community is that if we could just increase the efficiency of Tor, with crypto improvements or whatever, that it will make Tor faster).

This doesn’t mean that increases in bandwidth or efficiency are valueless. What is being increased is the number of users who can use the technology.

Also, I wanted to mention that the comparison to transportation infrastructure is a good one. However, for what its worth, roads are an even worst case of the diminishing returns of throwing more bandwidth at the problem because roads also exhibit a second property: peak-load. If you think about it, roads for most of the day and all night sit nearly empty. It is terrible economic efficiency to have a resource be vacant for most of the day, and completely congested for a few hours in the morning and late afternoon.

One explination we where given (as students) for it was that as the effective cost of the “good” came down due to more efficient utilisation of it, it became viable for others to use where it had previously been to expensive. It was further pointed out that demand usually does not go up in proportion to the effective reduction in cost but according to a power law, so you effectivly get a watershed point after which Jevons paradox applies.

You sometime here this refered to as the “cost of entry” or “cost of technology switch” or even “cost of (S) curve jump” effects (by marketing/managment speak persons when applied to new technology take up.

On another note with regards to increasing “efficiency” it generaly has an inverse relationshp to security…

That is the more efficiently a resource is utalized the more likley it is to leak information about it’s usage. This is seen in practice with things like timing and side channel attacks.

An example of this is things like implementations of AES being “unrolled” which cuases timing differences due to the CPU caching involved. The resulting changes due to cache hits can be seen on the network and as has been demonstrated the secret key extracted from the timing diffs.

Various papers have shown that TOR and equivalents are prone to this sort of effect. Which begs the question,

“If the current quite poor performance of the Tor anonymity network is improved such that it reaches a takeup watershed, will the security decrease proportionatly to the usage or worse?”

This sounded a lot like Jevon’s paradox to me.

Jevons paradox is a special case of the demand/supply model where a fall in price of a good, cased by a rise in conversion efficiency, results in a rise in demand high enough to increase the amount of raw good consumed. In my model of Tor I’ve assumed the total bandwidth available is static, so Jevons paradox doesn’t apply.