3 ms·

FWIW, Tor browser has had it disabled for years. Caching and anonymity are almost always at odds. For timing attacks, I think the required sample size of first

FWIW, Tor browser has had it disabled for years. Caching and anonymity are almost always at odds. For timing attacks, I think the required sample size of first connection to third party would be too large to reasonably exploit. You have to see if your first attempt does just a couple of TCP handshake messages shorter, future attempts would send the session ID from the first in client hello. There's too much between the third party and your user's browser for you to make any assumptions about just one loaded resource's TLS shortcut.

Klathmon 8y ago
> There's too much between the third party and your user's browser for you to make any assumptions about just one loaded resource's TLS shortcut. Are you assuming that or is there some testing you know of that can help back that up? Because I've heard of timing attacks happening over networks with a surprising amount of precision. Granted I'm inclined to believe you, it's my gut feeling as well, but I've been so very wrong about this in the past that I default to assuming there is no amount of latency or jitter that can hide a timing attack from a determined attacker.
- jerf 8y ago
  "Because I've heard of timing attacks happening over networks with a surprising amount of precision." They can, when you can issues thousands, millions, or even billions of attempts that are sufficiently statistically independent and then do statistics on the result. In this case, you want to see if the user has an open TLS session to a particular resource, but you only get one shot at the result, because after the first shot, now the user certainly has a TLS session open to the particular resource. So you have no opportunity to do many K/M/Grequests to nail down the differences and are swamped by other random events. Across a population of browsers you might be able to extract a small fraction of a bit per user, but you're certainly not getting anywhere near the full bit (yes they have open session/no they do not) on a per-user basis. While you can extract non-zero amounts of information I don't think you could count on getting any sort of useful information from it.
  - Klathmon 8y ago
    That's a really good point, thanks!
btown 8y ago
Consider that an attacker could find a number of websites hosted on EC2 us-east-1, and build statistics across not only all those websites from a single browser, but also from multiple attacked users with similar average RTTs to us-east-1. Deviations from the mean across similar users would be the flags. And with a phishing campaign, you don't need to be accurate all the time.

Klathmon 8y ago

> There's too much between the third party and your user's browser for you to make any assumptions about just one loaded resource's TLS shortcut. Are you assuming that or is there some testing you know of that can help back that up? Because I've heard of timing attacks happening over networks with a surprising amount of precision. Granted I'm inclined to believe you, it's my gut feeling as well, but I've been so very wrong about this in the past that I default to assuming there is no amount of latency or jitter that can hide a timing attack from a determined attacker.

jerf 8y ago
"Because I've heard of timing attacks happening over networks with a surprising amount of precision." They can, when you can issues thousands, millions, or even billions of attempts that are sufficiently statistically independent and then do statistics on the result. In this case, you want to see if the user has an open TLS session to a particular resource, but you only get one shot at the result, because after the first shot, now the user certainly has a TLS session open to the particular resource. So you have no opportunity to do many K/M/Grequests to nail down the differences and are swamped by other random events. Across a population of browsers you might be able to extract a small fraction of a bit per user, but you're certainly not getting anywhere near the full bit (yes they have open session/no they do not) on a per-user basis. While you can extract non-zero amounts of information I don't think you could count on getting any sort of useful information from it.
- Klathmon 8y ago
  That's a really good point, thanks!

btown 8y ago

Consider that an attacker could find a number of websites hosted on EC2 us-east-1, and build statistics across not only all those websites from a single browser, but also from multiple attacked users with similar average RTTs to us-east-1. Deviations from the mean across similar users would be the flags. And with a phishing campaign, you don't need to be accurate all the time.