Re: [Ace] Roman Danyliw's No Objection on draft-ietf-ace-coap-est-17: (with COMMENT)

[Jim Schaad <[e-mail]>]

A couple of comments below.  See [JLS]

-----Original Message-----
From: Roman Danyliw via Datatracker <[e-mail]> 
Sent: Monday, December 16, 2019 2:02 PM
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Subject: Roman Danyliw's No Objection on draft-ietf-ace-coap-est-17: (with COMMENT)

Roman Danyliw has entered the following ballot position for
draft-ietf-ace-coap-est-17: No Objection

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COMMENT:
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* Section 4.  Per “the DTLS connections SHOULD only be kept alive for EST messages that are relatively close to each other”, I think the text means that some EST messages are more likely to occur one after another.  It would be worth being clearer what these would be.

* Section 5.1. Per “These URIs are shorter than the ones in [RFC7030]”, does Table 1 imply that when using EST-coaps the “longer names” from RFC7030 wouldn’t be valid?
[JLS] This is being addressed via Alexey's discuss I think.

* Section 5.2  Per “The latter ones are deemed to expensive …”, was difficult to parse as the sentence prior has three things (instead of two).  Is this sentence referring to the “not specified functions” only?

* Section 5.3, Per “30% smaller payload for DER-encoded ASN.1”, if you can cite this metric, please do.
[JLS] Do you really need a metric on the difference between the size of raw binary vs base6 encoded binary?  It is just 3 bytes vs 4 bytes (i.e  4/3)

* Section 5.8.  Per “In summary, the symmetrically encrypted key is included in the encryptedKey attribute in a KEKRecipientInfo structure”, if this is done in a server-side key generation scenario, where is the client getting the key to decrypt the server computed key material?  Should the DecryptKeyIdentifier/ AsymmetricDecryptKeyIdentifier attributes be populated in the CSR per Sections
4.4.1.1/4.4.1.2 of RFC7030?
[JLS] That would be the discussion of these attributes in paragraph 3 (about the middle)?  Or are you looking for something more?

* Section 10.1.  Per “When server-side key generation is used, the constrained device depends on the server to generate the private key randomly, but it still needs locally generated random numbers for use in security protocols, as explained in Section 12 of [RFC7925].”, is the “security protocols” referenced here anything beyond DTLS?

* Section 10.1.  Per “In such occasions, checking the certificate revocation status or authorizing the client using another method is important for the server to ensure that the client is to be trusted.”

-- does this text suggest that expired+revoked certificates should not be used?
[JLS] Yes, a revoked certificate would most likely not be used.  However, my personal expectation is that this would map more directly to a database associated with the CA as it is possible that the manufacturer could have gone under and not be doing CRLs in any event.

Jim Schaad

-- to word-smith:
s/for the server to ensure that the client is to be trusted/for the server to raise its confidence that the client can be trusted/

* Section 10.1.  Per “More information about recommendations of TLS and DTLS
are included in   [BCP195]”, thanks for referencing BCP195.  Could you please
clarify with normative language if these recommendations SHOULD/MUST be followed?

* Editorial
- Section 4.  Per “Authenticating and negotiating DTLS keys requires resources on low- end endpoints and consumes valuable bandwidth”, I’m not sure this sentence is needed.  Technically, “authenticating and negotiating DTLS keys requires resources” on any endpoint.

- Section 4.
OLD: Given that after a successful enrollment, it is more likely that a new EST transaction will take place after a significant amount of time, NEW: Given that after a successful enrollment, it is more likely that a new EST transaction will not take place for a significant amount of time,

- Section 5.5. Typo.  s/successfull/successful/

- Section 5.8.  s/Such scenarios could be when it is …/Such scenarios apply when it is …/

- Section 5.8.  s/ client, or when the resources/client, when the resources/

- Section 5.8. s/Then the private key/The private key/