Re:Uptime Lab's CM4 Blade Adds NVMe, TPM 2.0 to Raspberry Pi
by duskwuff on Wednesday August 04, 2021 @04:15PM
(#28065737)
> I wonder if it can be used for things like better random number generation...
Too slow to be useful, and the BCM283x SoC already has an internal RNG:
https://github.com/torvalds/linux/blob/master/drivers/char/h...
> ... or hardware-accelerated hashing
The TPM is on a really slow bus (33 MHz, 4 bits, tons of wait states). Even without any hardware acceleration, hashing on the CPU is much faster.
Re:Uptime Lab's CM4 Blade Adds NVMe, TPM 2.0 to Raspberry Pi
by staticassertion on Wednesday August 04, 2021 @07:51PM
(#28067956)
You wouldn't hit a TPM every time you wanted a random number. Your OS would just use it when it wanted to seed its entropy pool.
This is particularly useful at boot when entropy is very low.
Re:Uptime Lab's CM4 Blade Adds NVMe, TPM 2.0 to Raspberry Pi
by megous on Wednesday August 04, 2021 @03:47PM
(#28065398)
TPMs are just SPI connected devices. You can add them to any SBC.
Hardware accelerated hashing would be severely limited by the SPI bus speed.
Re:Uptime Lab's CM4 Blade Adds NVMe, TPM 2.0 to Raspberry Pi
by simcop2387 on Wednesday August 04, 2021 @03:19PM
(#28065049)
I believe the 2.0 standard does support rng, but I;m not sure of the specifics. there might be some hashing functionality but the interface is going to be too slow for large data. I think it;s there to do integrity checks for bootloaders and such
But I wonder why it's included here. Maybe for secure storage of private keys? I'm guessing that's the desired purpose for TPM in a server setting.
Obviously I'm not super familiar with TPM. I wonder if it can be used for things like better random number generation or hardware-accelerated hashing. I'm guessing if it supported hashing from userspace, the cryptocurrency crowd would have been all over it already.