tor/changes/ticket19769

  o Major features (security):
    - Change the algorithm used to decide DNS TTLs on client and server side,
      to better resist DNS-based correlation attacks like the DefecTor attack
      of Greschbach, Pulls, Roberts, Winter, and Feamster).  Now
      relays only return one of two possible DNS TTL values, and clients
      are willing to believe DNS TTL values up to 3 hours long.
      Closes ticket 19769.
DefecTor countermeasure: change server- and client-side DNS TTL clipping The server-side clipping now clamps to one of two values, both for what to report, and how long to cache. Additionally, we move some defines to dns.h, and give them better names. 2017-01-02 20:55:39 +01:00			`o Major features (security):`
			`- Change the algorithm used to decide DNS TTLs on client and server side,`
			`to better resist DNS-based correlation attacks like the DefecTor attack`
			`of Greschbach, Pulls, Roberts, Winter, and Feamster). Now`
			`relays only return one of two possible DNS TTL values, and clients`
			`are willing to believe DNS TTL values up to 3 hours long.`
			`Closes ticket 19769.`