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    SubjectRe: /dev/random and /dev/psaux: too much entropy assumed?
       From: Florian Weimer <fw@cygnus.stuttgart.netsurf.de>
    Date: 30 May 1999 19:43:47 +0200

    After subtracting the timer interrupts, we get an average of over
    nine bits added on each /dev/psaux interrupt to the /dev/random pool.
    I don't think that there is that much entropy involved to justify this
    high value.

    The entropy estimation is based on the jitter in the timestamp clock for
    the interrupts. The dx,dy values from the mouse are folded into the
    entropy pool along with the timestamp information, but it's only the
    first, second, and third order derivitives of the timestamp which are
    used in estimating the entropy.

    What can influence the time that the interrupt comes in? A lot of
    things, including when/if the kernel has interrupts disabled, to how
    quickly or slowly the mouse is being moved around.

    - Ted

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