Weak Collision Resistance; . That's 1,200 times the number of grains of sand on the earth. Since this never occurred naturally in real world under normal conditions we can rule out securi. Supports cluster (automatically), custom seeds, custom alphabet. Git 2.11 has been released | Hacker News > >> Yes, the abbreviated hash that `git describe` produces is unique among > >> all objects (and objects are more than just commits) in the current > >> repo, so what matters for probability-of-collision is the total number > >> of objects - linus.git itself probably grows ~60000 objects per release. Universal Hash Functions Notation: Let [m] = {0, 1, 2, …, m - 1}. "The quick summary if you do not want to read this entire post is that the problem is really not that bad. Currently Reading. How long should a hash be to be absolutely secure? What happened today was a SHA-1 collision, not a preimage attack. Implementing our Own Hash Table with Separate Chaining in Java The git hash is made up of the following: The commit message. How does one achieve message integrtity? In-band deduplication for Btrfs [LWN.net] Indeed issuer and firm identifiers are presumably unique. $\begingroup$ What MD5 (or, ideally, a better hash function like SHA-2 or BLAKE2b) gets you is a short token that you can compare to later.Doing a byte-by-byte comparison involves reading both files entire contents from disk in order to compare them. Git can only store one half of the colliding pair, and when following a link from one object to the colliding hash name, it can't know which object the name was meant to point to. That is fifty thousand billion billion different commits, or fifty Zettacommits, before you have reached even a 0.1% chance that you have a collision. The First Collision for Full SHA-1 - SpringerLink If the input is longer than the output, then some inputs must map to the same output — a hash collision. the one being described) clashes with some other object in the first 15 hex chars is less than 1e-10, and currently a git repo tracking Linus', -stable and . When you take all these into consideration, hopefully you will begin to see how various actions might impact how the commit hash is formed. You only need to ensure that the hash function is so large that intentionally finding such collisions (a collision attack) is computationally infeasible. Chance of short SHA1 hash collision at 7 character hash string #2 - GitHub algesten on Nov 30, 2016. OJFord on Nov 30, 2016 . So, the probability of getting a collision decreases . code that was the equivalent of the entire Linux kernel history (3.6 million Git objects) and pushing it into one enormous Git repository, it would take roughly 2 years until that repository contained enough objects to have a 50% probability of a single SHA-1 object collision." - Scott Chacon