[lkml]   [2019]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH v24 01/12] Linux Random Number Generator
Stephan Müller <> 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.

 \ /
  Last update: 2019-11-24 05:53    [W:0.418 / U:3.672 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site