On Tue, Jul 1, 2014 at 7:14 AM, Corentin LABBE <clabbe.montj...@gmail.com> wrote:
> I am writing the PRNG driver for the Allwinner Security System SoC A20. The datasheet my search turned up (v1, Feb. 2013) just says: "160-bit hardware PRNG with 192-bit seed" and gives no other details. Do you have more info, perhaps from a more recent version or talking to the company? > I didn't know how to test it, so ... Unless you have much more info, I see no point in enabling it or writing a driver. You need a true hardware RNG to seed it, so you need random(4) /dev/random anyway and can just use /dev/urandom for PRNG requirements. Using this device might have an advantage if it is much faster or less resource-hungry than urandom, but I see nothing in its documentation that indicates it is. Anyway, do your applications need that? And, if so, would an application-specific PRNG be better yet? Then there is the crucial question of trusting the device. Kerckhoff's Principle (http://en.citizendium.org/wiki/Kerckhoffs%27_Principle) has been a maxim for cryptographers since the 19th century; no-one should even consider trusting it until full design details are made public and reviewed. Even then, there might be serious doubts, since hardware can be very subtly sabotaged and an RNG is a tempting target for an intelligence agency. (http://arstechnica.com/security/2013/09/researchers-can-slip-an-undetectable-trojan-into-intels-ivy-bridge-cpus/) That article discusses Intel and the NSA, but similar worries apply elsewhere. Allwinner is a fabless company, so you also need to worry about whatever fab they use. -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
