Re: [jose] I-D Action: draft-ietf-jose-json-web-encryption-09.txt

[Mike Jones <[e-mail]>]

Hi Richard,

Actually, there are four goals in play:

1.  GCM
2.  Efficient encoding for multiple recipients
3.  Header integrity protection
4.  Independent protection of each recipient's headers

Per my response to Russ, by giving up 4, we can achieve 1, 2, and 3.  (Credit goes to John Bradley for this solution.)

                                                            -- Mike

From: Richard Barnes [mailto:[e-mail]]
Sent: Thursday, April 25, 2013 11:14 AM
To: Mike Jones
Cc: Jim Schaad; [e-mail]
Subject: Re: [jose] I-D Action: draft-ietf-jose-json-web-encryption-09.txt

Mike,

Your facts are right, but your conclusions are wrong.

We have three mutually incompatible goals here:
1. GCM
2. Efficient encoding for multiple recipients
3. Header integrity

We can have any two of these, but not all three.  If we try to do all three (JWE-08), then we end up with the vulnerability identified in the CFRG thread.  So we need to choose which one to get rid of.

Getting rid of GCM is clearly not the right answer, as evidenced by the reaction in this thread.  There are clear, concrete use reasons to support multiple recipients, but not for header integrity.  And header integrity can be "polyfilled" with an optional feature, for those who are willing to break the multiple recipient case.  Clearly, header integrity is the weakest link here.

JWE-09 is the reductio ad absurdum of header integrity.  Let's do the logical thing and stop the absurdity.

--Richard



On Thu, Apr 25, 2013 at 2:48 AM, Mike Jones <[e-mail]<mailto:[e-mail]>> wrote:
Jim - I am surprised that you would say that my co-authors Eric Rescorla or Joe Hildebrand or the working group would advocate using AES GCM in a way that would result in severe security vulnerabilities - in particular, allowing attackers to obtain the XOR of the messages to multiple recipients encrypted using GCM - a vulnerability identified by the CFRG.

Not stating this in the document would seem to me to be highly irresponsible, given the brittleness of GCM in this regard, as identified by the CRFG.  As I said to Richard Barnes over dinner last night, while unpleasant, and possibly surprising to those who aren't familiar to how GCM actually works, as an editor, I viewed including the statement that "AES GCM MUST NOT be used when using the JWE JSON Serialization for multiple recipients, since this would result in the same Initialization Vector and Plaintext values being used for multiple GCM encryptions" as necessary, and "truth in advertising".

                                -- Mike

-----Original Message-----
From: [e-mail]<mailto:[e-mail]> [mailto:[e-mail]<mailto:[e-mail]>] On Behalf Of Jim Schaad
Sent: Wednesday, April 24, 2013 9:07 PM
To: Mike Jones
Cc: [e-mail]<mailto:[e-mail]>
Subject: Re: [jose] I-D Action: draft-ietf-jose-json-web-encryption-09.txt

Mike,

AES GCM MUST NOT be used when using the JWE JSON Serialization for
   multiple recipients, since this would result in the same
   Initialization Vector and Plaintext values being used for multiple
   GCM encryptions.

I doubt your co-authors would agree with this.
I doubt the working group with agree with this.
I know that at least one co-chair does not agree with this I can predict that the AD and IESG along with the security directorate would crucify me if I allowed this to stand in the document..

Jim



> -----Original Message-----
> From: [e-mail]<mailto:[e-mail]> [mailto:[e-mail]<mailto:[e-mail]>] On Behalf
> Of [e-mail]<mailto:[e-mail]>
> Sent: Tuesday, April 23, 2013 5:29 PM
> To: [e-mail]<mailto:[e-mail]>
> Cc: [e-mail]<mailto:[e-mail]>
> Subject: [jose] I-D Action: draft-ietf-jose-json-web-encryption-09.txt
>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
directories.
>  This draft is a work item of the Javascript Object Signing and
> Encryption Working Group of the IETF.
>
>       Title           : JSON Web Encryption (JWE)
>       Author(s)       : Michael B. Jones
>                           Eric Rescorla
>                           Joe Hildebrand
>       Filename        : draft-ietf-jose-json-web-encryption-09.txt
>       Pages           : 54
>       Date            : 2013-04-23
>
> Abstract:
>    JSON Web Encryption (JWE) is a means of representing encrypted
>    content using JavaScript Object Notation (JSON) data structures.
>    Cryptographic algorithms and identifiers for use with this
>    specification are described in the separate JSON Web Algorithms (JWA)
>    specification.  Related digital signature and MAC capabilities are
>    described in the separate JSON Web Signature (JWS) specification.
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-jose-json-web-encryption
>
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-ietf-jose-json-web-encryption-09
>
> A diff from the previous version is available at:
> http://www.ietf.org/rfcdiff?url2=draft-ietf-jose-json-web-encryption-0
> 9
>
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
> _______________________________________________
> jose mailing list
> [e-mail]<mailto:[e-mail]>
> https://www.ietf.org/mailman/listinfo/jose

_______________________________________________
jose mailing list
[e-mail]<mailto:[e-mail]>
https://www.ietf.org/mailman/listinfo/jose
_______________________________________________
jose mailing list
[e-mail]<mailto:[e-mail]>
https://www.ietf.org/mailman/listinfo/jose