
Quantum-secured blockchain - blopeur
https://arxiv.org/abs/1705.09258
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snakeanus
> current blockchain platforms rely on digital signatures, which are
> vulnerable to attacks by means of quantum computers

There are many digital signature schemes (such as SIDH, New Hope,
Lamport+Merkle, SPHINCS, etc) which are not vulnerable to any important
quantum attacks.

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andy_ppp
How do they work? Are they just difficult to write quantum algorithms for or
is there some fundamental mathematics involved that stops a quantum computer
enumerating the solutions?

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contravariant
To the best of my knowledge there's not even any known mathematical theorem
that would prevent such algorithms on regular computers. I don't see how this
would be any different for quantum computers.

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gizmo686
That is correct. Any proof that digital signatures are secure on classical
computers would imply P != NP.

Further, it is known that BQP (bounded error quantum polynomial time. The
quantum computer equivalent of P) is contained in PSPACE. However P=PSPACE is
still an open question. This means that we still do not have any theoretical
proof that quantum computers are more powerful that classical computers.

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tscs37
The blockchain itself is for most cryptocurrencies already quantum-proof,
since they rely on hashing blocks until some number of leading zeroes is met.
That is the blockchain part.

What the paper seems to target is quantum-proof account management, a problem
which atleast on the Ethereum blockchain is trivial to solve at the moment
with some inconvenience and with later Hardforks implementing the account
abstraction, will be part of how the chain works. Everyone can then just use a
Lamport/Merkle signature, SIDH, New Hope, whatever, as long as it can be
implemented on the EVM.

I'm not certain why we need to throw quantum-computing at the blockchain until
some arbitrary amount sticks that can be declared "secure".

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heheocoenev
I agree that we need to implement postquantum computing algo's for both
hashing (proof of work function) and signing (transaction authentication). I
don't agree we should build a QKD network of p2p fiber to er this. SIDH is
looking the most attractive for the postquantum signing, at least.

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powera
I call shenanigans! No way a six-page paper demonstrates "an experimental
realization of a quantum-safe blockchain platform that utilizes quantum key
distribution".

