[Cryptography] A TRNG review per day (week?): ATSHA204A has low entropy

Bill Cox waywardgeek at gmail.com
Thu Dec 11 17:30:22 EST 2014

On Thu, Dec 11, 2014 at 2:21 PM, R P Herrold <herrold at owlriver.com> wrote:
> On Tue, 9 Dec 2014, Bill Cox wrote:
> > I just did another simple test.  After cold-booting my Raspberry Pi, I
> > called "./haslet random" and recorded the 32-byte result.  I had the
> > update-seed parameter turned off
> Using an un-seeded RNG with the hashlet code requires patching
> out the protections which the code offers.  This seems a lot
> like complaining that it hurts when you stick a fork in your
> eye
> You were running something based on another's code, but
> after removing the in-built  guarding.  It is NOT:
>         ./hashlet random
> How is this a fair test?
> -- Russ herrold

Hi, Russ.  Especially if all you're using this device for is DRM of some
sort, feel free to use it exactly as Atmel recommends.  However, the EEPROM
seed is most likely a back-door.  I have to laugh at the phrased "unseeded
RNG" when talking about a hardware true random number generator.  There's
no such thing.

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