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Comment by GordonS | Hacker News Reader

I've read your comment 3 times, and I'm still not exactly sure what you are suggesting, or what the purported benefit is? (it's probably my poor interpretation, but I'd appreciate if you wouldn't mind expanding :)

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Site A can't see the cached resources of site B, because it would show that the user has visited site B if the resource is provided too fast. However, if the resource is provided with some delay, then site A assumes that site B hasn't been visited.

The current solution is to download the same thing twice. It is wasteful and I offer downloading it only once, but if site A asks for a resource for site B, the resource should not be returned immediately, but after a few ms so that site A gets the wrong conclusion.

It should work if site A can observe only the result of the request but can't check if a request happened or not.

Ah, right, I understand your point now. When sites determine if something is cached or not, are they doing it purely based on the time taken to load it?

Yes, as far as I've seen the issue explained. I'm not sure though so I'm asking if someone knows for a side-channel that would invalidate my solution.

This is based on trying to prevent profiling based on which fonts or versions of things are precached by behaving as if they are not cached, when in reality serving a local file with a simulated delay.

He wrote that: save bandwith and data caps.

He would lose performance but win more privacy.

I understand the purpose of caching well enough; what I didn't understand was the proposal was to delay returning data from the cache.

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