[Lake] Re: I-D Action: draft-ietf-lake-edhoc-psk-03.txt

["[e-mail]" <[e-mail]>]

Hello Gabriel,

I corrected some of the things you mentioned.

Shouldn't the names of the PRK_* be updated to the PSK workflow?
I mean PRK_3e2m should be renamed as PRK_3e, and PRK_4e3m should be renamed as PRK4e


Regarding the indexes of the PRK, we have been discussing if we should change the names or not, since there is no MAC being used. However, as it is right now, this draft specifies the differences with respect to RFC9528, and by changing the names, we would need to redefine all the keys, i.e., write it as an independent document (which is indeed an option and something to be discussed during the IETF).

where do the “resumption_psk_length” and “id_cred_psk_length” values from  come from? from the “external” PSK?

So, they should have enough length to avoid collisions. Rafa commented the following:

the rID_CRED_PSK should have "enough" length to reduce the probability of a collision but the drawback is that we may want to have a really short rID_CRED_PSK
Another option for this would be that the Responder chooses the new ID_CRED_PSK and include this in message_4. If the new ID_CRED_PSK is sent in message_4 , this also can signal that resumption PSK must be generated.

Best,

Elsa





________________________________
From: GABRIEL LOPEZ MILLAN <[e-mail]>
Sent: Friday, March 7, 2025 4:01 PM
To: [e-mail] <[e-mail]>
Cc: GABRIEL LOPEZ MILLAN <[e-mail]>
Subject: [Lake] Re: I-D Action: draft-ietf-lake-edhoc-psk-03.txt

Hi.

Just a few comments about the edhoc-psk-03 drafts ….

1. Introduction

s/nodes nodes/nodes

"EDHOC with PSK authentication benefits systems where .." --> Does suit the term "systems" in this senteces? Shouldn't be better to talk about uses cases? In fact, the next paragraph begins with "Another key use case...".

"In this case, the PSK is provisioned after the establishment of a previous EDHOC session by using EDHOC_Exporter (resumption PSK)." --> What is the meaning of "(resumption PSK)" here, Does it means that this paragraph describes the concept of resumption? or just points out that this PSK is the resumption PSK"? in this case I suggest:  "In this case, the PSK (resumption PSK) is provisioned after the establishment of a previous EDHOC session by using EDHOC_Exporter.

3. Protocol

s/a COSE_Key compatible authentication credential that contains the PSK/a COSE_Key compatible authentication credential that contains the external or resumption PSK

4. Key Derivation

Shouldn't the names of the PRK_* be updated to the PSK workflow?

I mean PRK_3e2m should be renamed as PRK_3e, and PRK_4e3m should be renamed as PRK4e

Probably the whole key derivation process description should be included here.

6.2

s/foruth/fourth


6.5

s/that that/that

s/The EDHOC protocol complies with this NIST requirement/The EDHOC-PSK protocol complies with this NIST requirement.

7

The resumption process implies a new EDHOC-(resumption)PSK exchange. Although obvious, It should be mentioned in the text.

where do the “resumption_psk_length” and “id_cred_psk_length” values from  come from? from the “external” PSK?

7.1

s/Implmentations/Implementations


Have a nice weekend.

Best regards, Gabi.



El 1 mar 2025, a las 14:59, [e-mail]<mailto:[e-mail]> escribió:

Internet-Draft draft-ietf-lake-edhoc-psk-03.txt is now available. It is a work
item of the Lightweight Authenticated Key Exchange (LAKE) WG of the IETF.

  Title:   EDHOC Authenticated with Pre-Shred Keys (PSK)
  Authors: Elsa Lopez-Perez
           Göran Selander
           John Preuß Mattsson
           Rafael Marin-Lopez
  Name:    draft-ietf-lake-edhoc-psk-03.txt
  Pages:   17
  Dates:   2025-03-01

Abstract:

  This document specifies a Pre-Shared Key (PSK) authentication method
  for the Ephemeral Diffie-Hellman Over COSE (EDHOC) key exchange
  protocol.  The PSK method enhances computational efficiency while
  providing mutual authentication, ephemeral key exchange, identity
  protection, and quantum resistance.  It is particularly suited for
  systems where nodes share a PSK provided out-of-band (external PSK)
  and enables efficient session resumption with less computational
  overhead when the PSK is provided from a previous EDHOC session
  (resumption PSK).  This document details the PSK method flow, key
  derivation changes, message formatting, processing, and security
  considerations.

The IETF datatracker status page for this Internet-Draft is:
https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-ietf-lake-edhoc-psk/__;!!D9dNQwwGXtA!SyHYdZ-gkvWueYwUCUZ6VuzjV4QIf6wL2_w5nKKNgfnxujt9lR2pZh87KMm35PpRZZ7XCt7DSmpjQvJ1S6L9uQ$

There is also an HTML version available at:
https://urldefense.com/v3/__https://www.ietf.org/archive/id/draft-ietf-lake-edhoc-psk-03.html__;!!D9dNQwwGXtA!SyHYdZ-gkvWueYwUCUZ6VuzjV4QIf6wL2_w5nKKNgfnxujt9lR2pZh87KMm35PpRZZ7XCt7DSmpjQvKZ1D4BgQ$

A diff from the previous version is available at:
https://urldefense.com/v3/__https://author-tools.ietf.org/iddiff?url2=draft-ietf-lake-edhoc-psk-03__;!!D9dNQwwGXtA!SyHYdZ-gkvWueYwUCUZ6VuzjV4QIf6wL2_w5nKKNgfnxujt9lR2pZh87KMm35PpRZZ7XCt7DSmpjQvIW-Mvjfg$

Internet-Drafts are also available by rsync at:
rsync.ietf.org<http://rsync.ietf.org>::internet-drafts


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-----------------------------------------------------------
Gabriel López Millán
Departamento de Ingeniería de la Información y las Comunicaciones
University of Murcia
Spain
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