Followup to: <[EMAIL PROTECTED]>
By author: Gaspar Sinai <[EMAIL PROTECTED]>
In newsgroup: linux.utf8
>
> I happy that you recognized that what I see the
> real problem with bi-di is - the non-reversability.
>
It's not just bidi, though. Virtually *any* display algorithm in use
today, including most of the ones for ASCII, are reversible (consider
tabs versus spaces, for example.)
I also think that you're making up a security issue where one doesn't
exist: what you have to guarantee is that no standard-compliant viewer
should be able to view the same code in such a way that it may be
interpreted differently by the viewing human.
Non-reversibility doesn't enter into this. Say, for example, that
you're signing a PDF document. A big part of PDF is to get different
PDF viewers to display the same document in the same way. However, it
is completely and utterly impossible to go from the display back to
the original document bits -- the display process *always* loses
information. The same thing is true for HTML, for example (consider
HTML comments, which aren't even displayable.) Consider ASCII
whitespace.
> I think not having bi-bi alrogithm, or having a revised
> bi-di algorthm, or an advisory secure one would solve a
> lot of issues. If there is a revised bi-di algorithm
> old documents might even be converted to the secure one
> somehow - algorithmically to the same view.
Actually, this would *result* in the security problem you're
complaining about.
I think you're barking up the wrong tree.
-hpa
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"Unix gives you enough rope to shoot yourself in the foot."
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