Re: draft-ietf-pkix-logotypes-06.txt

[Denis Pinkas <Denis.Pinkas@xxxxxxxx>]

Russ,

> We just posted an update to the logotypes draft.  There are two primary
> changes from the previous version.  First, we tried to be more clear about
> what is mandatory to implement and what is not.  

This is not yet clear enough. See below.

> Second, we added support for more than one hash function without having 
> to repeat a lot of data.
> 
> The loudest objections (as opposed to jokes) came from Microsoft.  Based on
> discussions with Trevor Freeman, I believe that Microsoft can accept this
> version.
> 
> We are still in Working Group Last Call.....

Since we are still in Working Group Last Call, here are my 12 comments on
that document.

1. Page 6. Section 3. Logotype data

"Implementations MUST support image data; however, support for audio data is
OPTIONAL." Audio is a good joke, in the same way, as pheromones. We are
supposed to deal with serious documents. Please delete.


2. Page 7. Section 4.1 Extension format

"Clients MUST support both direct and indirect addressing."

I disagree. If an end-user certificate is included in a signature, it may be
interesting to display the logotype even if the terminal is off-line.
Indirect addressing would mandate an on-line connection.

Replace with:

"Clients claiming to conform with this document SHALL support direct
addressing. Clients MAY also support indirect addressing."


3. Page 7. Section 4.1 Extension format

There is no text which states what the client should do whenever it is
unable to support a given logotype. Insert the following text:

"Whenever a client is unable to support a given logotype, no error SHALL be
reported and the client MUST behave as if there was no logotype included in
the certificate".


4. Page 8. Section 4.1.

      LogotypeData ::= SEQUENCE {
         image           SEQUENCE OF LogotypeImage     OPTIONAL,
         audio           [1] SEQUENCE OF LogotypeAudio OPTIONAL }

Since audio support should be suppressed, replace with:

      LogotypeData ::= SEQUENCE OF LogotypeImage


5. Page 7. Section 4.1.

We have:

      communityLogo   [0] EXPLICIT LogotypeInfo OPTIONAL,

      LogotypeInfo ::= CHOICE {
         direct          [0] LogotypeData,
         indirect        [1] LogotypeReference }

      LogotypeData ::= SEQUENCE {
         image           SEQUENCE OF LogotypeImage OPTIONAL,

No explanations are given on the text about what to do for a client when
there is more than one LogotypeImage present in a communityLogo.

First of all, a communityLogo may contain more than one logo which belongs
to one or more communities. However the client has no way to know whether
the LogotypeData includes different versions from the same logo (e.g. in
black and white or in color) or different logos.

The ASN.1 structure is not adapted to make that difference. Therefore it is
proposed to modify the ASN.1 syntax along the following way:

         communityLogos   [0] EXPLICIT CommunityLogos OPTIONAL,

CommunityLogos ::= SEQUENCE OF CommunityLogo

CommunityLogo ::= LogotypeInfo

In this way, clients can make their best efforts to support only one
instance of version for each CommunityLogo.


6. Page 9. Section 4.1.

      LogotypeImageInfo ::= SEQUENCE {
         fileSize        INTEGER,  -- In octets
         xSize           INTEGER,  -- In pixels
         ySize           INTEGER,  -- In pixels
         numColors       INTEGER } -- In bits

Text is missing to explain this structure. How is a grey scale indicated for
jpeg and for gif ???


7. Page 9. Section 4.1.

      LogotypeImageInfo ::= SEQUENCE {
         fileSize        INTEGER,  -- In octets
         xSize           INTEGER,  -- In pixels
         ySize           INTEGER,  -- In pixels
         numColors       INTEGER } -- In bits

It is of particular importance to say what means conformance to this
document for a client with respect to the number of pixels to support and
the colors to support.

It is proposed to add a sentence along these lines:

"Clients claiming to conform with this document SHALL support an image with
a minimum size of 48 pixels (xSize) by 32 pixels (ySize) in black and white
with X grey levels."


8. Page 9. Section 4.1.

      LogotypeImageInfo ::= SEQUENCE {
         fileSize        INTEGER,  -- In octets
         xSize           INTEGER,  -- In pixels
         ySize           INTEGER,  -- In pixels
         numColors       INTEGER } -- In bits

It would also be appropriate to say what to do when the image is in color
and that the client has no color display available. No display at all ?
Conversion into grey scale using which kind of transposition ?


9. Page 9. Section 4.1. Since audio is a joke, text and ASN.1 about audio
should be deleted.


10. Page 9. Section 4.1. The text states:

"Implementations MUST support both the JPEG and GIF image formats (with MIME
types of "image/jpeg" and "image/gif", respectively)"

I would guess that Animated GIF should not be supported. Could we say it ?


11. Page 10. Section 4.1.

      Community Logotype. If communityLogo is present, the logotype MUST
      represent the community to which the certificate issuer is
      affiliated. The communityLogo MAY be present in an end entity
      certificate, a CA certificate or an attribute certificate.

A certificate issuer may belong to more than one community. Replace: "the
community " by :"the community or the communities". 


12. Page 11. Section 5. Type of certificates

   Logotypes MAY be present in three types of certificates:

     - CA certificates
     - End-entity certificates
     - Attribute certificates

Why is there such a limitation ? CRL Issuers, OCSP responders or TSUs may
have logotypes present in their certificates.

Replace with : "Logotypes MAY be present in any type of certificate".


Denis



> 
> Russ