Your math is off a bit[0][1] but you're right, it's a vanishingly small probability of a single collision. This is fairly academic though, when you're talking a

Your math is off a bit[0][1] but you're right, it's a vanishingly small probability of a single collision. This is fairly academic though, when you're talking about an adversary exploiting weaknesses in the algorithm itself, and not a perfect PRF. [0] http://preshing.com/20110504/hash-collision-probabilities/ http://preshing.com/20110504/hash-collision-probabilities/ [1] http://www.wolframalpha.com/input/?i=%281+billion+*+7+billion+per+second+*+1000+years%29^2+%2F+%282+*+2^256%29 http://www.wolframalpha.com/input/?i=%281+billion+*+7+billio...