At 08:32 PM 9/13/2013, Jerry Leichter wrote:
If by server you mean one of those things in a rack at Amazon or Google or Rackspace - power consumption, and its consequence, cooling - is *the* major issue these days. Also, the servers used in such data centers don't have multiple free USB inputs - they may not have any.
More to the point, the servers in the data centers aren't going to let you plug things in to them, especially if you're just renting a virtual machine or cloud minutes and don't get to connect to the real hardware at all (which also means you're not going to be able to use disk drive timing.) A tablet computer has lots of sensors in it; even turning the cameras on at boot time and hashing the raw pixels should give you a reasonable chunk of entropy; you're not going to turn your virtual machine upside down and shake it like an Etch-A-Sketch.
I realize it's possible for somebody to try to manipulate this, but I've always assumed that ethernet packet timing ought to give you some entropy even so, and even though with virtual machines you may only get quantized versions of interrupt times. Startup processes are probably going to include pinging a router and a name server, or at least they could if you wanted.
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