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Re: signature construct (was: Re: [ietf-dkim] DKIM BOF -- draft charter and agenda)

2005-10-15 12:30:23

On Sat, 15 Oct 2005, Earl Hood wrote:

On October 14, 2005 at 12:08, Stephen Farrell wrote:

PS: Just so's I can reconstruct it for myself later, the construct
might end up something like:
   body-hash = Hash1(nonce, body)
   sig-bits  = Private-key(Hash2(nonce,header-stuff, body-hash))

Actually the "data" hash would be more like:

 data-hash = Hash1(nonce, header-stuff, body)
 sig-bits  = Private-key(Hash2(nonce, DKIM-Signature-field))

I.e. The digital signature is only on the DKIM-Signature field,
nothing else.

For comparison META Signatures is something like:
 data-hash = hash1(nonce, some-headers, body-part)
 ; body-part can be particular mime part (or several) or entire message body
 ; some headers is optional and typically include only Content-* fields
 sig-bits = Private-key(hash2(nonce, meta-parts, data-hash, header-stuff))
 ; where meta-parts is META-Signature field with sig segment cut out

META-Signature design itself allows for inclusion of header fields in
either way listed in previous email (together with body hash or together with signature itself) but I obviously prefer inclusion with signature.

--
William Leibzon
Elan Networks
william(_at_)elan(_dot_)net
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