Date: Wed, 11 Jul 2018 14:03:56 +0200 From: Dirk-Willem van Gulik <dirkx@webweaving.org> To: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Limits to seeding /dev/random | random(4) Message-ID: <3A988D26-7B08-4301-8176-B0ED8A559420@webweaving.org>
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When feeding /dev/random from hardware USB devices like Bill Woodcock’s design in PCB incarnation: https://13-37.org/de/shop/infinite-noise-trng/ Are there any caveats with regard to volume or speed of doing so ? Or is it always a plus ? Actual code at https://github.com/dirkx/infnoise/blob/master/software/libinfnoise.c line 122: if ((devRandomFD = open("/dev/random",O_WRONLY)) <0) .. error handling if (write(devRandomFD, bytes, length) != length) .. error handling And is there any case where length would not return the length written — it seems that the driver traps/ignores EINT, EAGAIN and short writes ? Or should one check the entropy available in /dev/random (how?) and hold off feeding it until it is low enough (this is what the infinite-trng seems to do on linux). With kind regards, Dw
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