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Let's suppose everyone has moved to content addressing. Considering all the amount of content generated every day, how much time would it take before real hash
by ComodoHacker 9y ago
Let's suppose everyone has moved to content addressing. Considering all the amount of content generated every day, how much time would it take before real hash collisions start to emerge?
- openasocket 9y agoThe number of 256-bit hashes you would have to generate in order to have a 50% that there's a duplicate in there is ~4*10^38. If we had a billion machines each generating a billion new hashes a second, it would take over 12 million years to get that many.
- GordonS 9y agoThis assumes computing power will remain constant; it won't. Also, it's highly likely that flaws will be found with the hash algorithm long before 12 million years are up.
- openasocket 9y agoI don't assume computing power is constant, just that the rate of content generation is more or less constant (I think a billion devices publishing a billion new pieces of content every second is a pretty reasonable upper bound). OP asked about the odds of collisions occurring by accident due to the sheer volume of content generated and published, not about attacker scenarios. Obviously we wouldn't use the same hash algorithm and setup for 12 million years, but the sheer absurdity of that length of time and that pace of content production shows this method will last, at least until flaws are found in SHA256.
- jononor 9y agoIPFS uses a multihash format, so that new hash functions can be introduced over time.
- ComodoHacker 9y ago>50% that there's a duplicate in ther I think even 0.01% would be enough to harm usability.
- DennisP 9y agoThe 50% chance he's referring to is the chance that, out of all that hashes that exist, there will be two hashes that match. He's saying that in his scenario it would be millions of years before there's even a single duplicate.