-=> Quoting Kurt Wismer to Paul Walker <=-
 KW> all true of course, but complicated... i'm sure there are other ways
 KW> around it too... after all, a crc is only unique for a given size, you
 KW> can have two different files with different sizes but the same crc...
    For the record. CRC's are not unique to their size. It is possible to 
create 2 different files of the same size with the same CRC. In addition, 
even 
"if" that were the case it would only be true of files smaller than the 
maximum size of the CRC (4 gigs for a 32bit CRC and for each byte over 4 gigs 
there would be 256 combinations to produce the same CRC). But that is not 
necessary to get into because it can be done with files 'considerably' 
smaller 
than that.
    One person wishing to prove this point produced an executable file with 
the same size and CRC of TBSCAN.EXE (sorry don't recall the version) in a 
couple of hours, back in the days when Bill Lambdin was discussing the 
virtues 
of the MD5 hash.
    Since the CRC is a calculation involving division, substituions of 
specific values in the equation can produce like results. (4/2=2 8/4=2 
/8=2)
Dave..
... THD ProScan support on the web, http://www.naples.net/~nfn03274
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