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0 pointsyuhong9y ago0 comments

Any 160-bit hash can generate a collision in 2^80 time though.

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3 comments · 1 top-level

rspeer9y ago· 2 in thread

I think the more important collision to worry about in 2^80 time is the Earth colliding with the Sun.

Our interstellar successors, if any, will probably have found something better than Git to use.

EDIT: I should be clear that I'm not making the usual silly claim that we don't need to worry about hashes being broken because they take forever to brute force. I'm saying that hashes will be broken, but not by brute forcing the entire hash space. A decade or so of cryptographic research will save you eons of compute time.

Dylan168079y ago

2^80 time is not as much as you think it is. The bitcoin network is currently calculating about 3 * 2^60 hashes per second. It can do 2^80 hashes in under a week.

The 2^80 space cost of doing a birthday attack is a lot more notable, but it's not unfeasible either. Yearly hard drive production is somewhere around 2^70 bytes. You're not pulling that attack off in the year 2017 but a big budget you could get probably get there in a few decades.

rspeer9y ago

Checking 2^80 hashes is indeed faster than I thought, thanks for the stats.

But checking 2^80 hashes and writing them to long term storage is still ridiculous. That budget should still go to hiring cryptographers, not buying hard drives.

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