+cc Weijie
On 1/7/20 6:43 PM, Mauro Condarelli wrote:
Thanks Daniel.
On 1/7/20 4:58 PM, Daniel Schwierzeck wrote:
On Tue, Jan 7, 2020 at 3:30 PM Mauro Condarelli mc5686@mclink.it wrote: ...
I also have problems with entropy pool in Linux, do you happen to know if (and how) MT7628 supports HWRNG?
what problems exactly?
Currently it takes a LOT of time to fill-up the entropy pool (over half an hour) and on first startup, when it has to generate ssh keys and other stuff system is virtually dead for that long.
if possible you should generate the host keys on the first SSH connection attempt. Otherwise the time of generation is predictable. If you use dropbear you can configure that.
On a embedded device you usually can only add randomness from interrupts sources to the entropy pool due to lack of disk or input devices. On a router the most interrupts are typically generated by drivers for ethernet and SPI/NAND/MMC controllers. You could use user-space daemons like haveged [1] to add more randomness from hardware events.
I tried that and it helps. I also found *traces* pointing in the direction of hardware support for RNG in my SoC; I have ca opy of the (badly incomplete) "MT7628 PROGRAMMING GUIDE" and it reports in "PWM1 Control register" an "interesting" field: RESV1 Select Random Generator mode. This males a lot of sense because this SoC is meant to implement Wireless routers, so crypto and random acceleration would be very useful. Unfortunately I don't have more precise information, hence the question.
maybe Weijie from Mediatek can tell if MT7628 has a HWRNG. But PWM1 sounds more like a pulse width modulator and shouldn't be related to a HWRNG.