Re: [Rats] Which Asymmetric algorithms for Charra?

["Panwei (William)" <[e-mail]>]

Hi Eric,

Got it. Now I have no questions.

Regards & Thanks!
Wei Pan

From: RATS [mailto:[e-mail]] On Behalf Of Eric Voit (evoit)
Sent: Thursday, August 13, 2020 3:20 AM
To: Panwei (William) <[e-mail]>
Cc: [e-mail]
Subject: Re: [Rats] Which Asymmetric algorithms for Charra?

Hi Wei Pan,

I don't think we need to define a key length for RSA.

  *   None of our RPCs are involved with generating a new key.  And we can always discover the length of the key by referencing the information from the keystore using known information (e.g., the certificate-name).
  *   Looking at the various SHA algorithms, they are actually different algorithms (since they produce different digest sizes).
  *   If we just match to what is in the TCG spec, we don't have to define/defend a different scoping than they have already made.

Thanks,
Eric

From: RATS <[e-mail]<mailto:[e-mail]>> On Behalf Of Panwei (William)
Sent: Wednesday, August 12, 2020 3:59 AM
To: Eric Voit (evoit) <[e-mail]<mailto:[e-mail]>>
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [Rats] Which Asymmetric algorithms for Charra?

Hi Eric,

Generally, I'm fine with your proposal. I have only one question below.

The TCG_Algorithm_Registry_r1p32_pub defines a variety of SHA algorithms named with key length as a suffix, it also defines the ID values for the different curves used for elliptic curve cryptography. But it seems like that the TCG_Algorithm_Registry_r1p32_pub doesn't specify the key length of the RSA algorithm. So do we need to define fine-granular RSA algorithms in the YANG module?

Regards & Thanks!
Wei Pan

From: RATS [mailto:[e-mail]] On Behalf Of Eric Voit (evoit)
Sent: Wednesday, August 12, 2020 6:52 AM
To: [e-mail]<mailto:[e-mail]>
Subject: [Rats] Which Asymmetric algorithms for Charra?

During the charra presentation at IETF 108, we said we were going to ask the following question to the list: "Should the algorithm set defined in YANG be reduced to just those asymmetric algorithms currently exposed in the current TPM 1.2 and 2 specifications?"

This is reflected seen in https://www.ietf.org/proceedings/108/slides/slides-108-rats-sessb-charra-update-00, Slide 7.

The proposal I would like to make is as follows:

  *   The TCG tracked algorithms supportable by a TPM should be the only ones included in a charra maintained list of YANG identities.

     *   This identity set needs to be extendable to new algorithms for any YANG models which augment charra.

  *   TCG Algorithm Registry Revision 01.32, Table 3 at https://trustedcomputinggroup.org/wp-content/uploads/TCG-_Algorithm_Registry_r1p32_pub.pdf contains the algorithms we should encode.

     *   There are other types of information within this table, and we might as well encode the full table within a YANG model.   That way we can explicitly make the scope of a "ietf-tcg-algs.yang" model the contents this TCG table encoded in YANG.

  *   The YANG model will indicate what TCG algorithms are deprecated by the IETF.  However identities for these deprecated algorithms from the TCG table will be assigned.  (e.g., SHA-1)


Are there any objections/questions/comments on this proposal?    I have a strawman YANG file posted at:
https://github.com/ietf-rats-wg/basic-yang-module/compare/master...ericvoit:patch-4<https://github.com/ietf-rats-wg/basic-yang-module/compare/master.....ericvoit:patch-4>

Henk also is thinking of encoding this same Table information within CDDL.  That could be inserted as an additional informational element of the document for where people prefer CDDL.

Eric

Eric Voit
Principal Engineer
.:|:.:|:. Cisco Systems, Inc.