Re: [tpmdd-devel] [RFC] tpm2-space: add handling for global session exhaustion

From: Dr. Greg Wettstein
Date: Tue Feb 14 2017 - 09:40:08 EST

On Fri, Feb 10, 2017 at 04:13:05PM -0500, Kenneth Goldman wrote:

Good morning to everyone.

> James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote on
> 02/10/2017 11:46:03 AM:
> > > quote: 810 milliseconds
> > > verify signature: 635 milliseconds

For those who may be interested in this sort of thing I grabbed a few
minutes and ran these basic verification primitives against a Kaby
Lake system.

Average time for a quote is 600 milliseconds with a signature
verification clocking in at 100 milliseconds. The latter is
consistent with what James found on his Skylake machine.

Latencies are still significant with things like container start

> > Part of the way of reducing the latency is not to use the TPM for
> > things that don't require secrecy:

> Agreed. There are a few times one would verify a signature inside the
> TPM,
> but they're far from mainstream:
> 1 - Early in the boot cycle, when there's no crypto library.
> 2 - When the crypto library doesn't support the required algorithm.
> 3 - When a ticket is needed to prove to the TPM later that it verified
> the signature.

I don't think there is any doubt that running cryptographic primitives
in userspace is going to be faster then going to hardware. Obviously
that also means there is no need for a TPM resource manager which has
been the subject of much discussion here.

The CoreOS paper makes significant reference to increased security
guarantees inherent in the use of a TPM. Obviously whatever uses
those are will have the noted latency constraints.

We have extended our behavior measurement verifications to the
container level so we offer an explicit guarantee that a container has
not operated in a manner which is inconsistent with the intent of its
designer. Getting the security guarantee we need requires that an
linkage to a hardware root of trust hence our concerns about hardware

Have a good day.

As always,
Dr. G.W. Wettstein, Ph.D. Enjellic Systems Development, LLC.
4206 N. 19th Ave. Specializing in information infra-structure
Fargo, ND 58102 development.
PH: 701-281-1686
FAX: 701-281-3949 EMAIL: greg@xxxxxxxxxxxx
"UNIX is simple and coherent, but it takes a genious (or at any rate,
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