[Okular-devel] md5 hash for annotation file name

[Markus Grabner]

Am Donnerstag, 11. September 2008 schrieb Brad Hards:
> On Thursday 11 September 2008 08:16:05 am Albert Astals Cid wrote:
> > A Dijous 11 Setembre 2008, Markus Grabner va escriure:
> > > I like Ivo's proposal to use QCryptographicHash, which supports MD4,
> > > MD5, and Sha1, so these are natural candidates.
> >
> > It's not an attacker, it's you having two files that collide and gets you
> > annotations from one to another.
>
> The probability of a collision (without actually trying to cause one) is 1
> in 2^64 for MD4 or MD5, and 1 in 2^80 for SHA1. I don't think that is too
> much of a problem.
>
> The more general issue is annotations for files that change. If you
> annotate your document, and then edit it, the annotations will be lost.
It depends on the application if this is a problem or not. If annotations are 
made to indicate proposed modifications to the author of a document, there is 
little reason to display the original annotations after the modifications 
have been implemented. And unless there are only minor changes, it is 
unlikely that the annotations will still be related to the updated content. 
If such a behaviour is desired, it is probably better to enter the 
annotations directly in the document processor (e.g., a LaTeX \marginpar{}).

The current implementation has the same problem (unless the size of the file 
is the same after a modification), but anyway I understood the annotation 
concept in okular to be designed for static files. Keeping track of 
modifications seems to be much harder, in particular if it should work 
transparently for different file formats. Are there any plans (or requests) 
to implement such a feature in okular?

	Kind regards,
		Markus


-- 
Markus Grabner - Computer Graphics and Vision
Graz University of Technology, Inffeldgasse 16a/II, 8010 Graz, Austria
Phone: +43/316/873-5041, Fax: +43/316/873-5050
WWW: http://www.icg.tugraz.at/Members/grabner