tor/changes/no_client_timestamps_024

  o Minor features (security, timestamp avoidance, proposal 222):
    - Clients no longer send timestamps in their NETINFO cells.  These were
      not used for anything, and they provided one small way for clients
      to be distinguished from each other as they moved from network to
      network or behind NAT. Implements part of proposal 222.
    - Clients now round timestamps in INTRODUCE2 cells down to the nearest
      10 minutes.  If a new Support022HiddenServices option is set to 0,
      or if it's set to "auto" and the feature is disabled in the consensus,
      the timestamp is sent as 0 instead. Implements part of proposal 222.
    - Stop sending timestamps in AUTHENTICATE cells. This is not such
      a big deal from a security point of view, but it achieves no actual
      good purpose, and isn't needed. Implements part of proposal 222.
    - Reduce down accuracy of timestamps in hidden service descriptors.
      Implements part of proposal 222.
Get ready to stop sending timestamps in INTRODUCE cells For now, round down to the nearest 10 minutes. Later, eliminate entirely by setting a consensus parameter. (This rounding is safe because, in 0.2.2, where the timestamp mattered, REND_REPLAY_TIME_INTERVAL was a nice generous 60 minutes.) 2013-09-18 00:05:48 +02:00			`o Minor features (security, timestamp avoidance, proposal 222):`
Stop sending the current time in client NETINFO handshakes. Implements part of proposal 222. 2013-09-17 23:55:43 +02:00			`- Clients no longer send timestamps in their NETINFO cells. These were`
			`not used for anything, and they provided one small way for clients`
			`to be distinguished from each other as they moved from network to`
Get ready to stop sending timestamps in INTRODUCE cells For now, round down to the nearest 10 minutes. Later, eliminate entirely by setting a consensus parameter. (This rounding is safe because, in 0.2.2, where the timestamp mattered, REND_REPLAY_TIME_INTERVAL was a nice generous 60 minutes.) 2013-09-18 00:05:48 +02:00			`network or behind NAT. Implements part of proposal 222.`
Remove the timestamp from AUTHENTICATE cells; replace with random bytes This isn't actually much of an issue, since only relays send AUTHENTICATE cells, but while we're removing timestamps, we might as well do this too. Part of proposal 222. I didn't take the approach in the proposal of using a time-based HMAC, since that was a bad-prng-mitigation hack from SSL3, and in real life, if you don't have a good RNG, you're hopeless as a Tor server. 2013-09-18 16:51:04 +02:00			`- Clients now round timestamps in INTRODUCE2 cells down to the nearest`
Get ready to stop sending timestamps in INTRODUCE cells For now, round down to the nearest 10 minutes. Later, eliminate entirely by setting a consensus parameter. (This rounding is safe because, in 0.2.2, where the timestamp mattered, REND_REPLAY_TIME_INTERVAL was a nice generous 60 minutes.) 2013-09-18 00:05:48 +02:00			`10 minutes. If a new Support022HiddenServices option is set to 0,`
			`or if it's set to "auto" and the feature is disabled in the consensus,`
Remove the timestamp from AUTHENTICATE cells; replace with random bytes This isn't actually much of an issue, since only relays send AUTHENTICATE cells, but while we're removing timestamps, we might as well do this too. Part of proposal 222. I didn't take the approach in the proposal of using a time-based HMAC, since that was a bad-prng-mitigation hack from SSL3, and in real life, if you don't have a good RNG, you're hopeless as a Tor server. 2013-09-18 16:51:04 +02:00			`the timestamp is sent as 0 instead. Implements part of proposal 222.`
			`- Stop sending timestamps in AUTHENTICATE cells. This is not such`
			`a big deal from a security point of view, but it achieves no actual`
			`good purpose, and isn't needed. Implements part of proposal 222.`
Round down hidden service descriptor publication times to nearest hour Implements part of proposal 222. We can do this safely, since REND_CACHE_MAX_SKEW is 24 hours. 2013-09-18 17:09:34 +02:00			`- Reduce down accuracy of timestamps in hidden service descriptors.`
			`Implements part of proposal 222.`