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Re: WebFonts WG discussions

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Fri, 7 May 2010 12:45:08 -0700
Message-ID: <w2hdd0fbad1005071245q789b4ea6l705702a40c5e76cc@mail.gmail.com>
To: "Levantovsky, Vladimir" <Vladimir.Levantovsky@monotypeimaging.com>
Cc: Matt Colyer <matt@typekit.com>, Erik van Blokland <erik@letterror.com>, "www-font@w3.org" <www-font@w3.org>
On Fri, May 7, 2010 at 11:35 AM, Levantovsky, Vladimir
<Vladimir.Levantovsky@monotypeimaging.com> wrote:
> On Friday, May 07, 2010 12:08 PM Tab Atkins Jr. wrote:
>>
>> On Fri, May 7, 2010 at 6:59 AM, Levantovsky, Vladimir wrote:
>> > Sorry for a delayed response. The reason I proposed to consider
>> adding
>> > checksum is because the WOFF file contains extended and private
>> metadata
>> > fields that are currently can be easily discarded – one can simply
>> cut them,
>> > zero-out related offset/length values in the WOFF header and modify
>> the WOFF
>> > length. I realize that adding checksum isn’t going to be a strong
>> protection
>> > against willful modifications, the same could be done with the
>> checksum
>> > present, but it would require a bit of an effort (to write the code
>> to
>> > recalculate the checksum).
>>
>> I believe that, by the time people are reaching into the file to cut
>> out tables and modify several values, recalculating a checksum is
>> trivial.  The operations and abilities required to do so are basically
>> the same.
>>
>
> Well, the key difference here is that I can discard metadata fields and zero-out their respective offset/length values using any HEX editor with no efforts. Recalculating a checksum does require writing a piece of code.

Anyone who knows enough to use a hex editor like that, though, can
certainly write the code.  The extra knowledge/effort that is required
to handle the checksum is so trivial as to be nonexistent.

~TJ
Received on Friday, 7 May 2010 19:46:00 UTC

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