Done HASH suggestion for v27

May 20, 2008
10,789
83
Syracuse, NY, USA
I don't think I knew about HASH. But I do think the following has been discussed before. The following statement (from HASH's help) is not true.

Code:
The hash value is a unique value corresponding to the content of a file. If two files have the same hash value and they're using SHA256, SHA384, or SHA512, then they have the same content (regardless of their file names or locations).
 
May 20, 2008
10,789
83
Syracuse, NY, USA
Should be "are very likely to have".
Probably should be left unsaid. Consider only 65-byte files (256^65 = 2^520 of them). There are 256^64 = 2^512 possible values for SHA512. That's an average of 256 files for each possible value of SHA512. ... hardly a good bet that two with the same SHA512 will be the same!
 

Charles Dye

Super Moderator
Staff member
May 20, 2008
4,275
78
Albuquerque, NM
prospero.unm.edu
Probably should be left unsaid. Consider only 65-byte files (256^65 = 2^520 of them). There are 256^64 = 2^512 possible values for SHA512. That's an average of 256 files for each possible value of SHA512. ... hardly a good bet that two with the same SHA512 will be the same!

And 255 times as many possible files with different hashes? Seems like pretty good odds to me.
 
Aug 23, 2010
595
8
It is known that hashes could collide. The thing is that probability of deliberately crafting such a hash is insignificant for a given purpose.