> -----Original Message----- > From: linux-crypto-owner@xxxxxxxxxxxxxxx <linux-crypto-owner@xxxxxxxxxxxxxxx> On Behalf Of > Jarkko Sakkinen > Sent: Wednesday, October 9, 2019 9:42 AM > To: Ken Goldman <kgold@xxxxxxxxxxxxx> > Cc: Safford, David (GE Global Research, US) <david.safford@xxxxxx>; Mimi Zohar > <zohar@xxxxxxxxxxxxx>; linux-integrity@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx; open > list:ASYMMETRIC KEYS <keyrings@xxxxxxxxxxxxxxx>; open list:CRYPTO API <linux- > crypto@xxxxxxxxxxxxxxx>; open list <linux-kernel@xxxxxxxxxxxxxxx> > Subject: Re: [PATCH] KEYS: asym_tpm: Switch to get_random_bytes() > > On Wed, Oct 09, 2019 at 10:33:15AM +0300, Jarkko Sakkinen wrote: > > On Wed, Oct 09, 2019 at 02:53:39AM +0300, Jarkko Sakkinen wrote: > > > On Wed, Oct 09, 2019 at 02:49:35AM +0300, Jarkko Sakkinen wrote: > > > > On Mon, Oct 07, 2019 at 06:13:01PM -0400, Ken Goldman wrote: > > > > > The TPM library specification states that the TPM must comply with NIST > > > > > SP800-90 A. > > > > > > > > > > https://trustedcomputinggroup.org/membership/certification/tpm-certified-products/ > > > > > > > > > > shows that the TPMs get third party certification, Common Criteria EAL 4+. > > > > > > > > > > While it's theoretically possible that an attacker could compromise > > > > > both the TPM vendors and the evaluation agencies, we do have EAL 4+ > > > > > assurance against both 1 and 2. > > > > > > > > Certifications do not equal to trust. > > > > > > And for trusted keys the least trust solution is to do generation > > > with the kernel assets and sealing with TPM. With TEE the least > > > trust solution is equivalent. > > > > > > Are you proposing that the kernel random number generation should > > > be removed? That would be my conclusion of this discussion if I > > > would agree any of this (I don't). > > > > The whole point of rng in kernel has been to use multiple entropy > > sources in order to disclose the trust issue. > > > > Even with weaker entropy than TPM RNG it is still a better choice for > > *non-TPM* keys because of better trustworthiness. Using only TPM RNG is > > a design flaw that has existed probably because when trusted keys were > > introduced TPM was more niche than it is today. > > > > Please remember that a trusted key is not a TPM key. The reality > > distortion field is strong here it seems. > > And why not use RDRAND on x86 instead of TPM RNG here? It is also FIPS > compliant and has less latency than TPM RNG. :-) If we go with this > route, lets pick the HRNG that performs best. > There's certification and certification. Not all certificates are created equally. But if it matches your specific requirements, why not. There's a _lot_ of HW out there that's not x86 though ... And: is RDRAND certified for _all_ x86 processors? Or just Intel? Or perhaps even only _specific (server) models_ of CPU's? I also know for a fact that some older AMD processors had a broken RDRAND implementation ... So the choice really should be up to the application or user. Regards, Pascal van Leeuwen Silicon IP Architect, Multi-Protocol Engines @ Verimatrix www.insidesecure.com
