Re: Security hole: Digital Signing + Downloadable fonts

[Marc Branchaud <marcnarc@xxxxxxx>]

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On Fri, 6 Dec 1996, PASZTOR Miklos wrote:
> 
>  My guess is that people generally  want to sign their own material 
>  produced on their PC, and not web pages and similar things downloaded 
>  from anywhere.
>  To tell the truth I do not see any reason to do that.
> 

That's not the way I read the problem.  Imagine a signed document served
up by a web server that says "you agree to pay $50023" but the line is in
a FONT command that tells your browser to display it in a particular font,
also on the web server.  Now, that font could do a mapping that translates
all 5's and 0's into spaces.  When you see the line in your browser then,
you'll read "you agree to pay $   23".

The document's signature would check out, so you might think that what
you're seeing is valid, and agree to pay $50023 without knowing it.

It's not a question of character sets, as the font just takes a value and
spews out a corresponding bitmap.  Whether the underlying encoding is
ASCII, UNICODE or some other thing makes no difference.  (Not to
trivialize character set issues -- I just don't think they quite apply
here.)

In my mind, this is also a separate issue from PKIs or digital signatures. 
If someone's going to intentionally set out to mislead people, there's not
much technology can do about it.  Even if a solution is found for this
particular problem, something else is bound to crop up.  Just because
someone can make an authenticable digital signature doesn't mean that they
can't lie.

		Marc

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