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From: Thorsten Blum To: Marek =?iso-8859-1?Q?Beh=FAn?= Cc: Bill Cox , Herbert Xu , "David S. Miller" , Nicolas Ferre , Alexandre Belloni , Claudiu Beznea , Linus Walleij , Ard Biesheuvel , stable@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Message-ID: References: <20260428101430.514838-3-thorsten.blum@linux.dev> <25ntssyy6t5uwxlwfpmrpzpcq6xv62l643hflf26hxi6lv5wqu@6vub6ysczjvd> Precedence: bulk X-Mailing-List: linux-crypto@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <25ntssyy6t5uwxlwfpmrpzpcq6xv62l643hflf26hxi6lv5wqu@6vub6ysczjvd> X-Migadu-Flow: FLOW_OUT Hi Marek, On Tue, Apr 28, 2026 at 01:18:08PM +0200, Marek Behún wrote: > Adding Bill Cox (waywardgeek) to the conversation. > > In the meantime Nack from me on this patch. > > From the original messages by Bill, it seems to me the part he was reviewing > was the ATSHA204A. > > In subsequent reply [1] Bill states > > While there is some evidence, there is still no convincing proof that there > is an entropy source in this device at all. There is some evidence that > Atmel has inserted a back-door. My advice is to avoid this line of parts > from Atmel for cryptographic use. > > In another message Peter Gutmann asks about ATECC108 [2] and Bill replies [3] > > This part uses the same language to describe the random number generator. > It is "high quality". I think that's pretty funny. > I would be interested in seeing if the new part can generate random numbers > continuously, or if it fails after it's EEPROM wears out like their other > parts. The use of an EEPROM seed is for PWN-ing your RNG, not making it > more secure. > > IMO the comments from the actual reviewer are more relevant than those of the > engineer working for the company which was accused of creating low quality > / backdoored TRNG, at least until the Atmel engineer provides some evaluation > code for the device (which they suggested they might do [4], but never did as > far as I can find). > > Maybe we can instead change the ATECC quality to something like 32? Does that > even make sense? > > Marek > > [1] https://www.metzdowd.com/pipermail/cryptography/2014-December/023857.html > [2] https://www.metzdowd.com/pipermail/cryptography/2014-December/023870.html > [3] https://www.metzdowd.com/pipermail/cryptography/2014-December/023879.html > [4] https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html Bill wrote in his review: "If I made no mistake (and I do make a lot), the "random" data from the Atmel ATSHA204A is highly predictable when you disable the seed update to EEPROM." However, the atmel-sha204a driver doesn't operate the device in that mode. It uses the Random command with seed updates enabled, which is also what the datasheet recommends for highest security: "Microchip recommends that the EEPROM seed always be updated." So the reported behavior doesn't reflect how the driver uses the device. Thanks, Thorsten