Re: [jose] RSASSA-PSS signature

My original message was not about encryption algorithms, it was about the RSASSA-PSS signature algorithm, which is not in JWA at all (I also don't see it listed in Mike's spreadsheet).

If you'd like to bring up encryption algorithms too, RFC 3447 states:
   Two encryption schemes are specified in this document: RSAES-OAEP and
   RSAES-PKCS1-v1_5.  RSAES-OAEP is recommended for new applications;
   RSAES-PKCS1-v1_5 is included only for compatibility with existing
   applications, and is not recommended for new applications.

10 years later, it may be appropriate to start encouraging movement away from RSAES-PKCS1-v1_5 rather than further encouraging its use.
Should the CFRG be asked for an opinion?

Mike

From: Mike Jones [mailto:Michael.Jones@microsoft.com]
Sent: Tuesday, March 12, 2013 4:12 PM
To: Richard Barnes; John Bradley
Cc: Peck, Michael A; jose@ietf.org
Subject: RE: [jose] RSASSA-PSS signature

Your statement that there are no MTI algorithms is actually incorrect.  The current JWA draft specifies REQUIRED (and RECOMMENED and OPTIONAL) algorithms, and indeed, as currently chartered, we are required to define the set of MTI algorithms.

The spreadsheet characterizing platform support for possible algorithms that John referred to is attached.  As you can see, RSA PKCS1-v1_5 is the only ubiquitously implemented asymmetric encryption algorithm.

                                                            -- Mike

From: jose-bounces@ietf.org<mailto:jose-bounces@ietf.org> [mailto:jose-bounces@ietf.org] On Behalf Of Richard Barnes
Sent: Tuesday, March 12, 2013 12:49 PM
To: John Bradley
Cc: Peck, Michael A; jose@ietf.org<mailto:jose@ietf.org>
Subject: Re: [jose] RSASSA-PSS signature

Since we are not putting requirements on algorithms (i.e., there is no MTI), there's no harm to having PSS in the algorithms list.  Only benefit!
--Richard

On Tue, Mar 12, 2013 at 3:24 PM, John Bradley <ve7jtb@ve7jtb.com<mailto:ve7jtb@ve7jtb.com>> wrote:
This has had a fair amount of discussion.   While I think almost everyone would prefer PSS, many implementations are going to be in scripting languages where the underlying libraries only support PKCS1-v1_5.

We did a survey of platforms to evaluate if we could move to PSS and the result lead us not to make PSS as the MTI.  In think that was reported out at the Atlanta IETF meeting.
Nat may be able to forward that to you, I don't have it handy.

If we were talking about starting from scratch and not building on existing platforms likely the answer would have been different.

The algorithms are extensible so PSS can be added.   The other consideration is that many of the people who care will be using ECESA signatures anyway.

John B.

On 2013-03-12, at 2:52 PM, "Peck, Michael A" <mpeck@mitre.org<mailto:mpeck@mitre.org>> wrote:

draft-ietf-jose-json-web-algorithms-08 includes RSASSA-PKCS1-v1_5 signatures but not RSASSA-PSS.

The Security Considerations states:
   While Section 8 of RFC 3447 [RFC3447] explicitly calls for people not
   to adopt RSASSA-PKCS1 for new applications and instead requests that
   people transition to RSASSA-PSS, this specification does include
   RSASSA-PKCS1, for interoperability reasons, because it commonly
   implemented.

Shouldn't RSASSA-PSS at least be included as an option?
I'm also not sure if I fully understand the interoperability concerns.  JWS is a new specification, so it makes sense to me to use whatever algorithms are currently considered best practice, without need to worry about backwards compatibility?

Mike

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