Last modified: 2007-10-27 21:20:11 UTC

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Bug 11702 - Current caching of rendered math formulas allows a tiny but non-zero chance of hash collisions resulting in a display of wrong formulas
Current caching of rendered math formulas allows a tiny but non-zero chance o...
Status: RESOLVED WONTFIX
Product: MediaWiki extensions
Classification: Unclassified
Math (Other open bugs)
unspecified
All All
: Lowest minor (vote)
: ---
Assigned To: Nobody - You can work on this!
:
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2007-10-18 20:18 UTC by Jens Seiler
Modified: 2007-10-27 21:20 UTC (History)
1 user (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Attachments

Description Jens Seiler 2007-10-18 20:18:03 UTC
As far as I can see the current implementation of the LaTeX rendering of mathematical formulas creates image files using the md5 hash of the latex string as filename.
Whenever a formula needs to be shown on a website the md5 hash of its latex string is calculated and the filesystem is being checked for a file of that name.
If no such file exists it will be created, otherwise the existing image file will be shown.

There is an astronomical but non-zero chance of two different formulas having the same md5 hash, resulting  in a wrong presentation of the second formula.
Even considering the birthday-paradox (http://en.wikipedia.org/wiki/Birthday_paradox) the chances should be rather small but maybe there's someone who nevertheless wants to fix this.
Comment 1 Roan Kattouw 2007-10-18 20:24:05 UTC
How about using {$pageid}-{$n} as a key, i.e. 1701-0 for the first formula on pageid 1701, 1701-1 for the second, etc. The drawback is that when a formula is added on top of a formula-rich article, the entire article's cache has to be purged (or moved?)

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