The same message isn't being encrypted with multiple GCM keys. It is only
encrypted with one key. Indeed, the proposed change that I discussed in my
earlier message to you that would enable the use of GCM with multiple
recipients would only encrypt the plaintext once. The originator and all
recipients use exactly the key stream - just as you said.
-- Mike
From: Russ Housley [mailto:[email protected]]
Sent: Thursday, April 25, 2013 2:40 PM
To: Mike Jones
Cc: [email protected]
Subject: Re: [jose] I-D Action: draft-ietf-jose-json-web-encryption-09.txt
Mike:
The same message encrypted with different GCM keys is a problem, but that is
not what ought to be going on here. I tried to explain that in my previous
message. The same GCM key is delivered to multiple recipients, perhaps using
different key management techniques. Since the originator and all of the
recipients use exactly the same key stream, this XOR concern does not arise.
Russ
On Thu, Apr 25, 2013 at 2:48 AM, Mike Jones
<[email protected]<mailto:[email protected]>> 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: [email protected]<mailto:[email protected]>
[mailto:[email protected]<mailto:[email protected]>] On Behalf Of Jim
Schaad
Sent: Wednesday, April 24, 2013 9:07 PM
To: Mike Jones
Cc: [email protected]<mailto:[email protected]>
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: [email protected]<mailto:[email protected]>
> [mailto:[email protected]<mailto:[email protected]>] On Behalf
> Of [email protected]<mailto:[email protected]>
> Sent: Tuesday, April 23, 2013 5:29 PM
> To: [email protected]<mailto:[email protected]>
> Cc: [email protected]<mailto:[email protected]>
> 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
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