How many different hashes can a 128 bit hash have?

Posted on 2006-05-13
Last Modified: 2010-10-05
Is the answer one as long as no collisions occur. Or have i got confused.
Question by:lukegriffiths110
    1 Comment
    LVL 32

    Accepted Solution

    I think your question is unclear....  But strictly speaking, a 128-bit hash can, by definition, have 2^128 (that's 2 raised to the 128th power) DIFFERENT values.  2^128 is a rather large number, something like 3.4 x 10^38 or 34 followed by 37 0's.

    If the question is really, what's the possibility that TWO DIFFERENT inputs will produce the SAME HASH, then that's a different question.  HASH algorithms are designed specifically to prevent that and so the possibility is quite remote.  I'm sure it's less than 2^128 but even if it is a few orders of magnitude less, the possibility would still be so remote so as to be of no consideration.

    Read some of the research on the particular hash algorithm you are talking about and there will some information about that subject.

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