furthermore, there are a few different revisions of this said encrypted file. each of these different revisions have an expected outcome. once you compute the files std dev and compare that with the known expected values, usually if it is within a generally close range, then that means the file is not corrupted.

That makes no sense at all.

Let's say the corruption that occurred was that every pair of bytes in the file was transposed -- eg. abcdefgh corrupted to badcfehg; a type of corruption that frequently occurs when files are written on big-endian machines and read on little-endian ones, or vice versa.

Pretty much every type of statistical analysis applied to the bytes of the file will simply not change at all.

Equally, if you change any 1 bit in any one byte of a (say) 1MB file, you'd need to calculate your standard deviation to an accuracy beyond the limits of double precision in order to detect the change.

You're flogging a dead horse.

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In reply to Re^5: Calculating corruption by BrowserUk
in thread Calculating corruption by james28909

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