Re: [dss] CMS (request for comments)

[Trevor Perrin <trevp@trevp.net>]

At 01:55 PM 4/26/2004 +0200, Andreas Kuehne wrote:
>Trevor !
>
>
>>>>>Why should I do client-side hashing in this case? The server will get 
>>>>>the complete content anyway?
>>>>
>>>>
>>>>Right - the benefits of client-side hashing (bandwidth-savings, 
>>>>privacy) can't be achieved.
>>>>
>>>>Actually, that's not quite true - the client could re-code the 
>>>>enveloping signature as a detached signature.  In other words, the 
>>>>client could remove the enveloped data.  This requires changing the 
>>>>length fields within the SignedData, so it's a little more surgery than 
>>>>just extracting SignerInfo's and certificates, but it's possible.
>>>
>>>
>>>In 1980 I built my first modem with 300 baud. This gadget would have 
>>>caused the need for this otptimization.
>>
>>
>>Well, I dunno - input documents could be large (for code-signing, say, or 
>>an S/MIME attachment).
>
>Well, thought about signed jars as detached signatures .. the classes 
>aren't included in the signature, are they ?

Yeah, I think you're right.

So I agree: there's not much use to the client recoding enveloping 
signatures as detached, to use client-side hashing.

But it's at least possible.  And we wouldn't have to do anything special in 
the protocol to support it.


Trevor