Messages in this thread | | | Date | Mon, 31 May 1999 15:03:04 -0400 (EDT) | From | "Theodore Y. Ts'o" <> | Subject | Re: /dev/random and /dev/psaux: too much entropy assumed? |
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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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