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Mathematical origin of 5% and 13% in WEP attacks
Not sure if this question fits in this forum but I'm sure to be corrected if I'm wrong, so here goes...
What is the origin of the 5% and the 13% probabilities in the WEP attacks? I have read the FMS and H1kari papers and understood them (I think). Now, I know that:
Prob of success = e^(-3) = 5% (when all X, Y and Z are not swapped)
and
Prob of success = e^(-2) = 13% (when two of X, Y and Z are not swapped)
I already know that they come from modeling the remaining KSA swaps as random, but how are these stats derived?
On Pg. 9 of the FMS paper there is a reference to the following formula:
e^(-2B/N)
where B is the # of the byte of the SK being attacked and N is the length of the keystream. But this formula doesn't seem to apply to my question because there aren't any logical values of B and N that make (2B/N) equal to 2 or 3.
Is there a general form of some crypto-analytical formula that applies here?
Thanks for the help!
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