https://bugs.documentfoundation.org/show_bug.cgi?id=93532
Bug ID: 93532
Summary: Image / CRC32 not enough ...
Product: LibreOffice
Version: 5.0.0.0.beta1
Hardware: Other
OS: All
Status: UNCONFIRMED
Severity: normal
Priority: medium
Component: graphics stack
Assignee: libreoffice-bugs@lists.freedesktop.org
Reporter: michael.me...@collabora.com
CRC32 is a great hash to check for large-scale data-corruption, but not to
ensure uniqueness - and LibreOffice builds a fair bit of its image comparison
foo on the idea that it is unique.
A crc32 hash is prone to collisions (due to its small size, any 32-bit hash
couldn't be better): it has 1/2 odds to loose an image for ~77000 comparisons:
http://preshing.com/20110504/hash-collision-probabilities (so, quite a real
number of real documents are expected to suffer).
We should use CRC64, or better - though the exact algorithm is fairly
immaterial - but having more precision would help, while keeping this a single
integer type rather than a more complex wrapper task.
Marco is looking into this.
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