| From | Sandy Harris <> | Date | Sun, 24 Nov 2019 12:51:19 +0800 | Subject | Re: [PATCH v24 01/12] Linux Random Number Generator |
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Stephan Müller <smueller@chronox.de> wrote:
> In an effort to provide a flexible implementation for a random number > generator that also ...
As usual, some of your proposals make considerable sense to me & others do not, at least on first reading. I may have more comments after reflecting some.
Meanwhile, a couple of things jump out at me:
> (a) When an interrupt occurs, the high-resolution time stamp is mixed > into the LFSR. ... > > (b) HID event data like the key stroke or the mouse coordinates are > mixed into the LFSR. ... > > (c) Device drivers may provide data that is mixed into the LFSR. ...
Why into the LFSR instead of into the entropy pool?
> The LRNG allows the TRNG and secondary DRNG mechanism to be changed > at runtime.
Why? This strikes me as pointless complication.
> * high performance of interrupt handling code: The LRNG impact on the > interrupt handling has been reduced to a minimum. On one example > system, the LRNG interrupt handling code executes within an average > of 65 cycles whereas the existing /dev/random on the same device > takes about 97 cycles when measuring the execution time of > add_interrupt_randomness().
Assuming you do this without sacrificing the input mixing, this would be worth submitting as a separate patch. Saving cycles on every interrupt definitely looks worth doing.
> * lockless LFSR to collect raw entropy
This too.
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