Quantum Computing and Bitcoin - page 3.

mixoftix

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Quote from: aliashraf on November 25, 2018, 06:27:27 AM

Wrong. There is no shortcut for sha2 and if it would be ever possible to find such a shortcut the whole bitcoin blockchain security will become void and you don't need to wait for QC to bring it down.

misunderstood. the SHA256 is not broken in output. what I wrote above is about the weakness in providing input for the SHA256 - because of weakness in random number generation. this is much more about vulnerabilities that exist in implementation stages of a secure platform - not the Math behind it. so we need to know how QC could influences in the structure of providing (and predict) input for SHA256 (or any other hash algorithm).

UPDATE:
we all know several online/offline bitcoin address generators that only run random function in javascript / server-side script. better solutions make the user to move her mouse to reach better amount of randomness. as I know we have no control over quality of randomness in bitcoin protocol. hope the paper bellow help:

http://www.mixoftix.net/knowledge_base/security/Key_Generation_with_Verifiable_Randomness.pdf

aliashraf

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Always remember the cause!

Quote from: mixoftix on November 25, 2018, 05:51:56 AM

Quote from: tromp on November 25, 2018, 04:34:35 AM

Quote from: bones261 on November 25, 2018, 03:04:16 AM

I think if we are at the point in technology that a QC can be made that can break SHA256 in a relatively trivial manner

Wrong; quantum computers need to run for 2^80 steps to find a private key mapping to a given 160 bit public key. That will remain infeasible for decades to come.

however the threat of QC is 51% attack, not directly breaking the key-pairs but while cryptographers think in probability space (2^80) of breaking something secure (in theory), there are Cryptanalysis methods out there to find shortcuts (in practice) and decrease the steps they need to pass:

https://en.wikipedia.org/wiki/Cryptanalysis

the most important point of failure that I see in asymmetric encryption is running a Random Function in key generation stage. providing real randomness is one of the hardest problems that I ever seen - because what you think is random at first sight, in fact carries a hidden pattern inside. so most of the time random number generation is where Cryptanalysis begin their job from.

Wrong. There is no shortcut for sha2 and if it would be ever possible to find such a shortcut the whole bitcoin blockchain security will become void and you don't need to wait for QC to bring it down.

mixoftix

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Quote from: tromp on November 25, 2018, 04:34:35 AM

Quote from: bones261 on November 25, 2018, 03:04:16 AM

I think if we are at the point in technology that a QC can be made that can break SHA256 in a relatively trivial manner

Wrong; quantum computers need to run for 2^80 steps to find a private key mapping to a given 160 bit public key. That will remain infeasible for decades to come.

however the threat of QC is 51% attack, not directly breaking the key-pairs but while cryptographers think in probability space (2^80) of breaking something secure (in theory), there are Cryptanalysis methods out there to find shortcuts (in practice) and decrease the steps they need to pass:

https://en.wikipedia.org/wiki/Cryptanalysis

the most important point of failure that I see in asymmetric encryption is running a Random Function in key generation stage. providing real randomness is one of the hardest problems that I ever seen - because what you think is random at first sight, in fact carries a hidden pattern inside. so most of the time random number generation is where Cryptanalysis begin their job from.

tromp

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Quote from: bones261 on November 25, 2018, 03:04:16 AM

I think if we are at the point in technology that a QC can be made that can break SHA256 in a relatively trivial manner

Wrong; quantum computers need to run for 2^80 steps to find a private key mapping to a given 160 bit public key. That will remain infeasible for decades to come.

bones261

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Quote from: ABCbits on November 25, 2018, 02:43:07 AM

ECDSA/secp256k1 is quantum-resistance as long as it's public key isn't known, which means users should be fine as long as they never re-use their Bitcoin address and Quantum computer isn't fast enough to find out it's private key before the transaction got confirmed/fully propagated to all nodes.

But there are proposal to use cryptographic signature which is quantum resistant, even though AFAIK there's huge trade-off such as far larger signature size and longer verification time.

I think if we are at the point in technology that a QC can be made that can break SHA256 in a relatively trivial manner, "ordinary computers" and network technology will be at the point that a larger signature size wouldn't be a problem either. Or are we still going to be fretting that someone's raspberry pi that they bought in 2009 should still be able to run a full node while only connecting with a 56K modem?

ABCbits

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Crypto Swap Exchange

ECDSA/secp256k1 is quantum-resistance as long as it's public key isn't known, which means users should be fine as long as they never re-use their Bitcoin address and Quantum computer isn't fast enough to find out it's private key before the transaction got confirmed/fully propagated to all nodes.

But there are proposal to use cryptographic signature which is quantum resistant, even though AFAIK there's huge trade-off such as far larger signature size and longer verification time.

8CommaClub

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Quote from: bones261 on November 24, 2018, 09:26:20 PM

Quote from: 8CommaClub on November 24, 2018, 09:18:15 PM

I

Quote from: bones261 on November 24, 2018, 09:09:56 PM

Quote from: 8CommaClub on November 24, 2018, 08:50:01 PM

If Quantum Computing is released into the wild and starts to attack bitcoin , what measures would we see to mitigate these attacks?

Hope some miners can also get a quantum computer to compete with mining and switch to an algorithm for the keys that would take the QC longer than it's expected Quantum decoherence time by a factor of billions upon billions.

What if the government controls the Quantum computer , and there isn't anyone to fight back? Would that spell the end of Bitcoin? And if there is , would it be necessary to move to QC resistant cryptography?

Back to the drawing board. If any entity gets control of 51% of the mining and there is no way to wrest back control, then Bitcoin is insecure and virtually worthless.

if this did happen and bitcoin did bring down the banks , so there is no "currency" system , i wonder what would come next.

bones261

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Quote from: 8CommaClub on November 24, 2018, 09:18:15 PM

I

Quote from: bones261 on November 24, 2018, 09:09:56 PM

Quote from: 8CommaClub on November 24, 2018, 08:50:01 PM

If Quantum Computing is released into the wild and starts to attack bitcoin , what measures would we see to mitigate these attacks?

Hope some miners can also get a quantum computer to compete with mining and switch to an algorithm for the keys that would take the QC longer than it's expected Quantum decoherence time by a factor of billions upon billions.

What if the government controls the Quantum computer , and there isn't anyone to fight back? Would that spell the end of Bitcoin? And if there is , would it be necessary to move to QC resistant cryptography?

Back to the drawing board. If any entity gets control of 51% of the mining and there is no way to wrest back control, then Bitcoin is insecure and virtually worthless.

8CommaClub

jr. member

Activity: 118

Merit: 3

I

Quote from: bones261 on November 24, 2018, 09:09:56 PM

Quote from: 8CommaClub on November 24, 2018, 08:50:01 PM

If Quantum Computing is released into the wild and starts to attack bitcoin , what measures would we see to mitigate these attacks?

Hope some miners can also get a quantum computer to compete with mining and switch to an algorithm for the keys that would take the QC longer than it's expected Quantum decoherence time by a factor of billions upon billions.

What if the government controls the Quantum computer , and there isn't anyone to fight back? Would that spell the end of Bitcoin? And if there is , would it be necessary to move to QC resistant cryptography?

bones261

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Activity: 1806

Merit: 1827

Hope some miners can also get a quantum computer to compete with mining and switch to an algorithm for the keys that would take the QC longer than it's expected Quantum decoherence time by a factor of billions upon billions.

8CommaClub

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Activity: 118

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If Quantum Computing is released into the wild and starts to attack bitcoin , what measures would we see to mitigate these attacks?

Topic: Quantum Computing and Bitcoin - page 3. (Read 1057 times)