First draft of the ballot comments on the new amendment

[Greg Hitchcock]

I've not had a chance to look at the code to verify this one way or another. It seems to me it would be wrong to not zero out the CheckSumAdjustment in the head table. I will not be able to look at this right away, but hope to soon.

GregH

-----Original Message-----
From: mpeg-OTspec at yahoogroups.com [mailto:mpeg-OTspec at yahoogroups.com] On Behalf Of 'Levantovsky, Vladimir' vladimir.levantovsky at monotype.com [mpeg-OTspec]
Sent: Friday, April 22, 2016 7:15 AM
To: Hin-Tak Leung <htl10 at users.sourceforge.net>
Cc: mpeg-OTspec at yahoogroups.com
Subject: [mpeg-OTspec] Re: First draft of the ballot comments on the new amendment

Dear Hin-Tak,

Thank you again for reviewing the draft ballot comments and for your proposal. A change you proposed aims to clarify/correct the existing standard and can be made via ballot comments. However, I'd like to hear from someone at Microsoft confirming the issue you uncovered since a similar correction would have to be made in the OT spec hosted online. If we receive a confirmation of the proposed change before Apr. 27 I will add it as yet another ballot comment, otherwise we'd have to postpone it until next major revision. 

Thank you,
Vlad

> On Apr 21, 2016, at 9:22 PM, Hin-Tak Leung <htl10 at users.sourceforge.net> wrote:
> 
> Dear Vlad,
> 
> Thanks for putting it all together. Whether it is appropriate as a 
> ballot comment now or a more involved revision later, to put in a 
> format closer to your draft, I propose that
> 
> under clause
> "5.7.1 DSIG  Digital signature table" ,
> 
> paragraph
> "Format 1: For whole fonts, with either TrueType outlines and/or CFF 
> data",
> 
> item
> "1. If there is an existing DSIG table in the font,",
> 
> in the list of 5 steps under item 1, deleting step "4. Zero out the 
> file checksum in the head table.",
> 
> and renumbering
> "5. Add the usFlag (reserved, set at 1 for now) to the stream of bytes"
> as
> "4. ....".
> 
> 
> The reason of change is to align the algorithm description in the spec with the most widely used implementation of signing and checking from Microsoft. For signing, as noted, there are a few 3rd party implementations e.g. from Fontlab and Dalton Maag; for checking, perhaps the only implementation is Microsoft's (chktrust.exe and the older Font Validator are regarded as the same, as they have a same wintrust mssipotf backend).
> 
> Hin-Tak


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