This seems reasonable to me.

I'm interested to see a specific take on encryption.


- m&m

Matt Miller - <[email protected]>
Cisco Systems, Inc.

On Aug 17, 2012, at 15:58, Richard L. Barnes wrote:

> Hey all,
> 
> At IETF 84, I suggested that we take another look at what header information 
> gets integrity-protected and what doesn't.  The main issue being that in 
> multiple-recipient or multiple-signer scenarios, there's unnecessary 
> duplication of data if recipient- or signer-specific information is in the 
> integrity-protected header.
> 
> Following some on what Bob Wyman proposed this afternoon, I would like to 
> propose that we split the set of header fields into some logical groupings:
> 1. Top-level fields that require integrity protection (e.g., cty or a digest 
> algorithm parameter)
> 2. Top-level fields that do not require integrity protection (e.g., x5c)
> 3. Fields that are specific to a signer (e.g., jwk)
> 4. Fields that are specific to a recipient (e.g., epk)
> 
> In this taxonomy, only fields of type (1) need to be base64-encoded for to 
> preserve their serialization, and fields of type (3) and (4) could be 
> gathered together into the moral equivalent of SignerInfo and RecipientInfo 
> objects.  All this makes the JSON serialization a lot cleaner, for example:
> 
> {
>    "type": "S",
>    "header": "[base64-type1]",
>    "params": { /* type2 */ },
>    "content": "[base64-content]",
>    "signers": [
>        { /* type3 */ }
>    ]
> }
> 
> You can also imagine a reasonable compact serialization, something like:
> 
> S.[base64-type1].[base64-type2].[base64-content].[base64-signer1].[base64-signer2].
>  ...
> 
> That encoding even has the benefit that the multi-signer case doesn't add any 
> overhead over the single-signer case, except for maybe a couple of "." 
> characters. (Obviously, you would want some structure on how the signer info 
> gets serialized, but that's another level of detail down.  You could imagine 
> something like "[signer-header].[public-key].[signature-value]".)
> 
> The additional structure might seem like it's more work to parse, but I don't 
> think it's really that bad.  Given a parsed JOSE object "obj":
> 1. Decode obj.header and add its fields to obj.params
> 2. Look through "signers" / "recipients" to find one we understand
> 3. Verify / decrypt content using signer/recipient info and parameters
> 
> There are several details to be worked out -- most critically, which fields 
> go in which groupings -- but I thought I would throw out the general idea for 
> comment before diving into the details.
> 
> Cheers,
> --Richard
> 
> 
> 
> 
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