That was my original point. However, I now realize how much of a
nightmare that would be.
On 5/9/2016 5:37 AM, Luca Testoni wrote:
On 06/05/2016 19:48, Russell Leidich wrote:
But to answer your question, if we assume that the TRNG resides in the
kernel, I see no way in which an acoustic attack could defeat it, even
if the implementation sourced its randomness exclusively from the
microphone, as too much audio precision would be required to create a
predictable byte stream of any significant length in a realistic server
environment with lots of fan noise and multipath arrival issues. So
unless you're trying to attack a purely audio TRNG in a recording studio
-- and probably not even then -- this route seems hopeless.
Alternatively, you could try to attack a timer-based TRNG by shooting
sound at the booting machine in the hopes that the sound device would
send incoming sample packets to main memory on a predictable schedule,
but this, too, seems hopeless because even ensuring timing correlation
between timestamp counters on different cores is a perpetual annoyance
to software developers; hoping to sync the audio and core clocks is much
harder. The very existence of the RDTSCP instruction, which reads the
timestamp on a specified core, is evidence of this difficulty.
Maybe could be attacked conversely, by an acoustic isolation of the
entropy noise sound device?
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