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Comment by WorldMaker | Hacker News Reader

Almost feels like by the time git finally transitions to SHA-256 some bitcoin miner somewhere will have a solved preimage weakness on SHA-256.

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Thankfully existing Bitcoin ASICs don’t pose much of a threat because they’re only good for sha256(sha256(Bitcoin block)).

If a practical pre-image attack on SHA-256 comes around we have bigger problems than git.

Obviously the concern is not the ASICs themselves but the ASIC designers. (Using miners here in the colloquial sense of human collectives/corporations backing the machines than than the specific sense of the raw machines themselves.)

Yes, a practical preimage weakness in SHA-256 is a nightmare scenario with huge implications to the rest of internet security beyond just get. It's why I sometimes can't sleep at night knowing how much energy bitcoin spends daily on a continuous massively distributed partial preimage attack on SHA-256.

> how much energy bitcoin spends daily on a continuous massively distributed partial preimage attack on SHA-256.

I would not be concerned about this. The way the asics operate is they discard the results. Also, the hashes are random strings which don't compress very well, so storing trillions upon trillions of them (for later analysis) is not practical.

Again, the point of the fear is not the specifics of current operations (ASIC details; which y'all are talking about as if all of the miners are using the same hardware), but the fear of future operations and that there's an enormous industrial preimage attack effort at all. One that we can see in real time, in global energy consumption graphs.

Maybe you find "cold comfort" that because we can watch it in real time if someone discovers a weakness we will also watch its repercussions and the subsequent horrifying fall in real time, too, but I certainly don't.

Addition modulo 2 paired with xor is a motherfucker ie a very difficult problem. That’s not even considering rotation of intermediate results.

I think the work they're doing to migrate to SHA-256 also includes not hardcoding the hashing algorithm so much into the code, so that it has some forwards compatibility if they need to change again in future.

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