128 bit hashes are “expect your first collision when each human buys 2305 iPhones, all with one terabyte storage, and then fills them up with photos that are an average of 1MB in file size”

https://en.wikipedia.org/wiki/Birthday_attack

http://www.wolframalpha.com/input/?i=2%5E64%20%2F%20%288e9%2...