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Re: minor suggestions in 3.2 (CipherData)

From: Joseph Reagle <reagle@w3.org>
Date: Tue, 4 Sep 2001 09:24:01 -0400
To: Amir Herzberg <AMIR@newgenpay.com>, "Xml Encrypt (E-mail)" <xml-encryption@w3.org>
Message-Id: <20010904132402.37DC0875DF@policy.w3.org>
On Monday 03 September 2001 02:33, Amir Herzberg wrote:
> Suggested new text:
> The optional set of ds:DigestMethod and ds:DigestValue elements are
> provided for ensuring the integrity of the encrypted data, by providing a
> digest (hash) computed over the data to be encrypted (plaintext). See
> section 5.7 of the algorithm specification for more information.

Ok, in new revision: 1.43; I should of done this from these minutes (also 
note we didn't quite understand that PlainData proposal.


Eastlake: I think he's trying to make it easier to denote what should be 
encrypted -- and make it clear that the DigestMethod and DigestValue apply to 
the plaintext not the ciphertext.

Reagle: I hope it's clear in the spec that DigestValue is over the plaintext. 
Otherwise this seems like an application issue to me (how it internally 
designates which sections to process)? I asked him to explain it a bit more 
on the list, so we'll roll this forward.

> I think it'll also be good to add description of the relevant processing to
> section 4, I can suggest some text.

Once Don sends text for reverting back to not using DigestMethod/DigestValue 
in the clear (I hope you saw Schaad's arguments [1]), I agree we should add 
some text about nonce, and digest processing.

[1] http://www.w3.org/Encryption/2001/Minutes/0720-Redwood/minutes.html

Proposal: DigestMethod/DigestValue Removal, Jim Schaad

Schaad: believes Herzberg wanted integrity, and something about the plaintext 
as it was before encryption. For the same reasons that Finney raised earlier 
about signature over plaintext, Schaad doesn't like plaintext being in the 
clear, should be encrypted as part of the CipherData; otherwise it allows for 
guessing of the original text if insufficient randomness exists.

Group: discussion of earlier approach of having integrity be part of the 
algorithm URI, people felt this led to too many algorithms identifiers. 
Present approach not liked for reasons stated.

Reagle: a poll was taken for Jim?s proposal: 5 supported Jim?s proposal and 2 
supported the current status. Eastlake suggested the proposal to be further 
discussion in the list.

Schaad: Proposed this as an optional element: If one wants integrity checks, 
then provide a new URI. Action Schaad: send proposal for integrity to list 
within the week with the necessary changes. Otherwise, need a use case 
(Herzberg engage Schaad in discussion) of the initial problem was, so we can 
understand the application where it applies (understanding now that it was 
wanted to have the digest value outside)
Received on Tuesday, 4 September 2001 09:24:04 UTC

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