Subject: Re: [pkix] WGLC for draft-ietf-pkix-certimage-06

From: "Pope, Nick" <[email-masked]>
Date: Thu, 25 Feb 2010 09:05:12 -0000

Paul,

Having been negative about this standard, following on from work in ETSI on
visual representation of signatures I am now fully supportive of this work
and believe it is important that it goes ahead.

There is a need for a way of visually representing the certified identity
which is easily comprehensible by untrained human users.  This can be used
in by a signatory as visible mark when signing a document, and also can be
easily visually checked by the relying party against the certificate when
verifying the signature.  Whilst the necessary identity information may be
in the existing X.509 fields its interpretation requires expertise beyond
the capabilities of most users who are ignorant of X.509 technology.  The
CA, by including a visible graphic with the certificate based on the
proposed Certimage, provides a visual representation of the certificate
which can be appropriate to the context in which the certificate is being
used and hence easily comprehensible to all parties involved in a
transaction as well as being trustworthy.

When looking at the practical usage of certificates this in fact improves
security as it addresses the human interface where many of the many of the
risks lie in obfuscation of meaning through complexity.

Nick

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
> Paul Hoffman
> Sent: 24 February 2010 18:44
> To: [email-masked]
> Subject: Re: [pkix] WGLC for draft-ietf-pkix-certimage-06
> 
> Greetings again. I continue to oppose this document as a new standard.
> 
> The document assumes that giving users better pictures will help those
> users make security choices. We have years of experience with RFC 3709,
> and none of that experience supports that assumption. The argument that
> "the earlier format wasn't expressive enough" is not supportable, given
> that none of the common web browsers or email clients even bothered with
> the earlier format. The need for this document is speculative, at best.
> 
> Further, the document adds three new complex display formats with
> completely insufficient security considerations about how displaying
> malicious forms of those formats can cause security-essential software to
> fail. Avoiding putting these types of issues in the Security
> Considerations section does a grave disservice to the security community
> and makes us look hypocritical, given how often we force other protocols
> to put more detail in their Security Considerations section.
> 
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