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Miller" , "Nicolas Ferre" , "Alexandre Belloni" , "Claudiu Beznea" , =?UTF-8?Q?Marek_Beh=C3=BAn?= , "Linus Walleij" Cc: stable@vger.kernel.org, linux-crypto@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Message-Id: In-Reply-To: <20260428101430.514838-3-thorsten.blum@linux.dev> References: <20260428101430.514838-3-thorsten.blum@linux.dev> Subject: Re: [PATCH v2] crypto: atmel-sha204a - drop hwrng quality reduction for ATSHA204A Content-Type: text/plain Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260428_031824_555038_818F0073 X-CRM114-Status: GOOD ( 11.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 28 Apr 2026, at 12:14, Thorsten Blum wrote: > Commit 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to > lowest possible") reduced the hwrng quality to 1 based on a review by > Bill Cox [1]. However, despite its title, the review only tested the > ATSHA204, not the ATSHA204A. > > In the same thread, Atmel engineer Landon Cox wrote "this behavior has > been eliminated entirely"[2] in the ATSHA204A and "this problem does not > affect the ATECC108 or the ATECC108A (or the ATSHA204A)"[3]. > > According to the official ATSHA204A datasheet [4], the device contains a > high-quality hardware RNG that combines its output with an internal seed > value stored in EEPROM or SRAM to generate random numbers. The device > also implements all security functions using SHA-256, and the driver > uses the chip's Random command in seed-update mode. > > Keep 'quality = 1' for ATSHA204, but drop the explicit hwrng quality > reduction for ATSHA204A and fall back to the hwrng core default. > > [1] > https://www.metzdowd.com/pipermail/cryptography/2014-December/023858.html > [2] > https://www.metzdowd.com/pipermail/cryptography/2014-December/023852.html > [3] > https://www.metzdowd.com/pipermail/cryptography/2014-December/023886.html > [4] > https://ww1.microchip.com/downloads/en/DeviceDoc/ATSHA204A-Data-Sheet-40002025A.pdf > > Fixes: 8006aff15516 ("crypto: atmel-sha204a - Set hwrng quality to > lowest possible") > Cc: stable@vger.kernel.org > Signed-off-by: Thorsten Blum Reviewed-by: Ard Biesheuvel