Re : [HW_RNG] How to use generic rng in kernel space

[moreau francis]

Michael Buesch wrote:
> The dataflow is as follows:

> HW-RNG -> userspace RNGD (through /dev/hwrng) -> the daemon
> checks it for sanity and puts it back into the kernel through
> /dev/random -> Your driver gets the data from the /dev/random
> entropy pools.

Is that also true for embedded systems ? I mean we may not found
any rngd on these systems.

One other question now: suppose that others drivers need to use
random data during their inits. At this time userspace appli still not
have been started. How does it work ?

> This is very neccesary, because your HW-RNG may fail and
> so you may unintentionally use non-random data, if you use
> the random data from the RNG directly.
> The data _must_ go through userspace rngd, which does FIPS
> sanity checks on the data.

Well I'm working on a secure SOC which have a randown hardware
which is supposed to return true random data. I understand that 
some self tests on the random data are needed but doing them in 
userspace is suprising.

thanks

Francis



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