42 upvotes, 5 direct replies (showing 5)
View submission: Don't invest recklessly
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Comment by Truffle_Shuffle_85 at 30/11/2017 at 11:30 UTC
65 upvotes, 4 direct replies
I was just envisioning this scenario the other day. It would feel like futuristic ship wreck hunters, using quantum computers to dig up once lost coins. Could be an interesting point whenever quantum computers become relatively accessible.
Comment by kjj9 at 09/12/2017 at 07:39 UTC
3 upvotes, 0 direct replies
I wouldn't bet on that happening in my lifetime. Probably not my kids either.
Most bitcoin keys are known only by hash, and hashing is very resistant to quantum attacks. Basically, there are general purpose quantum algorithms that solve *any* computation problem in, roughly, the square root of the time needed to solve it otherwise. Those can be used to answer the question "What is at least one of the private keys that corresponds to a public key that solves this known hash?"
The tricky part is that these algorithms work on circuits. What is a circuit, in this context? It is a device with no concept of time. There are no loops, no memory, no control structures. You set the inputs and the outputs converge on the answer.
This is most emphatically **not** how we build hashing devices. All of our hash functions have loops, which need to be unrolled to build a circuit. And by "unrolled", I mean physically. Doing 80 passes? You need 80 physical stages. Combining or mixing the bits along the way? You need more gates to tie it together. Using a lookup table or an initialization vector? God help you...
We do not possess the technology to build a hashing circuit today using conventional electronics. Even if we were willing to throw our biggest HPC clusters at the problem, I'm not even sure if our current computers are powerful enough to even design a hypothetical one. A handfull of unrolls and you've got more gates than we've ever put on a chip, and RIPEMD160 has 80 iterations.
Oh, and did I mention that it needs to be a *quantum* circuit? I think the world record for quantum gates in a coherent device can still be counted with one of your shoes on.
Comment by AuRelativity at 30/11/2017 at 13:59 UTC
1 upvotes, 0 direct replies
dibs on my coins.
Comment by FowlyTheOne at 30/11/2017 at 14:38 UTC
1 upvotes, 2 direct replies
What is the effort to crack a adress with current Hardware ? Are there some Infos somewhere?
Comment by ThatBitcoinGuyy at 30/11/2017 at 10:32 UTC
1 upvotes, 0 direct replies
oh wow that's a good point I never heard before. All of those dead wallets with a ton of btc will be accessible in the future.