Subject: [smime] Double base64 encoding unavoidable in enveloped messages?

From: Nelson B Bolyard <[email-masked]>
Date: Tue, 08 Jun 2010 10:57:37 -0700

Thunderbird's developers have received complaints about the relative size of
enveloped messages, as compared to the same message sent in plain text.
Investigation has shown that the message production

- creates the entire un-enveloped message, with any binary attachments
base64 encoded, then
- envelopes it, then
- base 64 encodes the enveloped message.

As some developers read it, this is the right/only way to do it.
They see the double-encoding as unavoidable.
It surely is wasteful of bandwidth and storage.
Is this double base64 encoding unavoidable?
Or is there something being overlooked here?

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From: Russ Housley <[email-masked]>
Date: Tue, 08 Jun 2010 14:22:02 -0400

This has been discussed several times over the last few years, and there
is agreement that the double-encoding ought to be avoided.  There is not
agreement about which one out to be eliminated.  The consequences are
different based on your deployment environment.

Russ

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From: "Jim Schaad" <[email-masked]>
Date: Wed, 9 Jun 2010 16:45:40 -0700

There are several things that you can look at.

1.  Emit and look for the binary smime capability.  This will allow you to
not do the inner base 64 encoding step which is the most likely to save you
one wrapping.  I have not been looking at active smime messages recently,
but most current clients should be doing this.

2.  If you would not normally do the outer wrapping, then you can omit doing
that.  While almost all current gateways and routers can deal with 8-bit
content, it is possible that some still exist that need 7-bit content and
thus the base64 encoding.

Jim

> -----Original Message-----
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> Of Nelson B Bolyard
> Sent: Tuesday, June 08, 2010 10:58 AM
> To: [email-masked]
> Subject: [smime] Double base64 encoding unavoidable in enveloped
> messages?
> 
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---

From: Peter Gutmann <[email-masked]>
Date: Thu, 10 Jun 2010 18:52:11 +1200

>There are several things that you can look at.

Also, hasn't support for binary data been a MUST for many years now?  I
remember this from some time ago... I haven't done a full archaeological
investigation but RFC 3851 from 2004 already says (section 3.1.2):

  S/MIME implementations MUST be able to deal with binary MIME objects.
   
(followed by text on not using base64).

Peter.

---

From: Nelson B Bolyard <[email-masked]>
Date: Fri, 11 Jun 2010 10:43:09 -0700

On 2010-06-09 23:52 PDT, Peter Gutmann wrote:
>> 1.  Emit and look for the binary smime capability.  This will allow you
>> to not do the inner base 64 encoding step which is the most likely to
>> save you one wrapping.  I have not been looking at active smime
>> messages recently, but most current clients should be doing this.
> 

Thanks, Jim & Peter.  This gives me what I need.