On Wed, 2019-10-16 at 19:25 +0300, Jarkko Sakkinen wrote: > On Wed, Oct 16, 2019 at 08:34:12AM -0400, James Bottomley wrote: > > reversible ciphers are generally frowned upon in random number > > generation, that's why the krng uses chacha20. In general I think > > we shouldn't try to code our own mixing and instead should get the > > krng to do it for us using whatever the algorithm du jour that the > > crypto guys have blessed is. That's why I proposed adding the TPM > > output to the krng as entropy input and then taking the output of > > the krng. > > It is already registered as hwrng. What else? It only contributes entropy once at start of OS. > Was the issue that it is only used as seed when the rng is init'd > first? I haven't at this point gone to the internals of krng. Basically it was similar to your xor patch except I got the kernel rng to do the mixing, so it would use the chacha20 cipher at the moment until they decide that's unsafe and change it to something else: https://lore.kernel.org/linux-crypto/1570227068.17537.4.camel@xxxxxxxxxxxxxxxxxxxxx/ It uses add_hwgenerator_randomness() to do the mixing. It also has an unmixed source so that read of the TPM hwrng device works as expected. James
