hash-collision

I want to know the probability of getting duplicate values when calling the GetHashCode() method on string instances. For instance, according to this blog post, blair and brainlessness have the same hashcode (1758039503) on an x86 machine. Large. (Sorry Jon!) The probability of getting a hash collision among short strings is extremely large . Given a set of only ten thousand distinct short strings drawn from common words, the probability of there being at least one collision in the set is approximately 1%. If you have eighty thousand strings, the probability of there being at least one

For each of our binary assets we generate a MD5 hash. This is used to check whether a certain binary asset is already in our application. But is it possible that two different binary assets generate the same MD5 hash. So is it possible that two different strings generate the same MD5 hash? For a set of even billions of assets, the chances of random collisions are negligibly small -- nothing that you should worry about. Considering the birthday paradox , given a set of 2^64 (or 18,446,744,073,709,551,616) assets, the probability of a single MD5 collision within this set is 50%. At this scale,

I've implemented a BloomFilter in python 3.3, and got different results every session. Drilling down this weird behavior got me to the internal hash() function - it returns different hash values for the same string every session. Example: >>> hash("235") -310569535015251310 ----- opening a new python console ----- >>> hash("235") -1900164331622581997 Why is this happening? Why is this useful? Martijn Pieters Python uses a random hash seed to prevent attackers from tar-pitting your application by sending you keys designed to collide. See the original vulnerability disclosure . By offsetting the

This probably never happened in the real-world yet, and may never happen, but let's consider this: say you have a git repository, make a commit, and get very very unlucky: one of the blobs ends up having the same SHA-1 as another that is already in your repository. Question is, how would Git handle this? Simply fail? Find a way to link the two blobs and check which one is needed according to the context? More a brain-teaser than an actual problem, but I found the issue interesting. I did an experiment to find out exactly how Git would behave in this case. This is with version 2.7.9~rc0+next