On: The birthday paradox in action: calculating the probability of a hash collision

[dbaupp]

The formula given at the end of the article implies that to have a 5% chance of a collision you would need 3.87e23 objects. (SHA-1 is 160 bits.) Even storing 1 trillion objects gives a collision probability of 3e-19.

So this is unlikely to be a concern, ever.

[bigiain → dbaupp]

Hmmm, I wonder how many objects are currently stored in S3? And what rate that's rowing at? Or how many documents Google has stored in bigtable?

But yeah, 160 bits is probably "enough" :-)