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[REBOL] Re: Question about checksum/secure

From: brett:codeconscious at: 20-Nov-2001 1:49

Thanks Holger and Ladislav,
> No, hashing is a many-to-one operation, mapping from an infinite space > (arbitrarily long string series) to a finite space (string series of > length 20), so there always has to be the chance of collisions. > > The chance of a collision is very small though, especially if you > deal with a small number of values, say, less than a billion billion > billion :-). For any two arbitrary strings to have the same checksum > the chance is 1/(2^160). For at least one collision among n strings > the chance is n/(2^160) (for n <= 2^160, obviously).
Hm a billion billion billion, guess it will be a while before my hardward threatens that, however I suppose some rarely used collision detection is in order. Next (and hopefully last) question then is, is the checksum/secure method something that could change? I was thinking of using it for example to generate a filename by doing checksum/secure on the content of a text file, but I think the question is useful for understanding encryption keys as well. Many thanks. Brett.