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Topic: In light of the NSA's disclosure about ECC, how is cryptocurrency affected? (Read 2655 times)

legendary
Activity: 2142
Merit: 1010
Newbie
The effective bit length is actually 136 bits since good algorithms like SHA 256 will require 2^(bit length/2) computations to brute force a single hash. This effective bit length will also change as the difficulty increases because miners will need to search through more nonces when there is a higher difficulty, so the bitcoin network would adjust to a quantum miner so blocks would still come out at around 10 minutes per block. So if we double the bit length by switching to SHA512, the effective bit length will also double so this will essentially make the quantum miners not anymore powerful than classical miners.

Frankly saying, it looks like you randomly put N, N/2 and 2N into different places trying to guess the correct formula. Maybe read the quoted whitepaper first? When the difficulty goes up quantum computers will get even a bigger advantage because of increased leverage (from 17 billion to trillions).
sr. member
Activity: 318
Merit: 260
One Time Pad without re-use.
staff
Activity: 3458
Merit: 6793
Just writing some code
I don't see where it says where it uses 68 bits. It says that it must search through on average 2^68 nonces. From what I understand, this does not mean that it is only 68 bits and that the number of nonces to search through will increase with a higher difficulty.

It means exactly this - effective hash width is 68 bits. Sorry, can't provide formal proof, just google around.
The effective bit length is actually 136 bits since good algorithms like SHA 256 will require 2^(bit length/2) computations to brute force a single hash. This effective bit length will also change as the difficulty increases because miners will need to search through more nonces when there is a higher difficulty, so the bitcoin network would adjust to a quantum miner so blocks would still come out at around 10 minutes per block. So if we double the bit length by switching to SHA512, the effective bit length will also double so this will essentially make the quantum miners not anymore powerful than classical miners.
legendary
Activity: 2142
Merit: 1010
Newbie
I don't see where it says where it uses 68 bits. It says that it must search through on average 2^68 nonces. From what I understand, this does not mean that it is only 68 bits and that the number of nonces to search through will increase with a higher difficulty.

It means exactly this - effective hash width is 68 bits. Sorry, can't provide formal proof, just google around.
staff
Activity: 3458
Merit: 6793
Just writing some code
Really? Can you back that up with maybe some research?

Last I checked, the only thing that makes quantum computers more efffective at hashing is grover's algorithm, which practically reduces the bit length by half. For the same security, the bit length can just be doubled, so using SHA512 instead of SHA256 on a quantum computer is the same as SHA256 on a classical computer.

Check the quote from the whitepaper upthread. In layman terms, SHA512 won't help, because at current difficulty Bitcoin operates only on 68 bits, the other zillion bits are completely irrelevant.
I don't see where it says where it uses 68 bits. It says that it must search through on average 2^68 nonces. From what I understand, this does not mean that it is only 68 bits and that the number of nonces to search through will increase with a higher difficulty.
legendary
Activity: 2142
Merit: 1010
Newbie
Really? Can you back that up with maybe some research?

Last I checked, the only thing that makes quantum computers more efffective at hashing is grover's algorithm, which practically reduces the bit length by half. For the same security, the bit length can just be doubled, so using SHA512 instead of SHA256 on a quantum computer is the same as SHA256 on a classical computer.

Check the quote from the whitepaper upthread. In layman terms, SHA512 won't help, because at current difficulty Bitcoin operates only on 68 bits, the other zillion bits are completely irrelevant.
staff
Activity: 3458
Merit: 6793
Just writing some code
Come-from-Beyond,
so let's assume you have a quantum computer that you can use to mine BTC.
Can you use it to disrupt the mining process or not?

Yes, with a QC you can invalidate last 1000 blocks, generate 20000 empty blocks and stop mining leaving the others with 20-year block times.
Really? Can you back that up with maybe some research?

Last I checked, the only thing that makes quantum computers more efffective at hashing is grover's algorithm, which practically reduces the bit length by half. For the same security, the bit length can just be doubled, so using SHA512 instead of SHA256 on a quantum computer is the same as SHA256 on a classical computer.
legendary
Activity: 1176
Merit: 1005
Decentralized Asset Management Platform
I'm not talking about banks man. I'm worried about public transportations, people's sensitive data and so forth.
You could say I'm being paranoid a bit. But, again, if such a thing would be used for the bad you would not care about your BTC wallet.
legendary
Activity: 2142
Merit: 1010
Newbie
and as I said, bitcoin would be our last concern.

This is ostrich policy. Banks won't be attacked by agencies that will get QCs.
legendary
Activity: 1176
Merit: 1005
Decentralized Asset Management Platform
Come-from-Beyond,
so let's assume you have a quantum computer that you can use to mine BTC.
Can you use it to disrupt the mining process or not?

Yes, with a QC you can invalidate last 1000 blocks, generate 20000 empty blocks and stop mining leaving the others with 20-year block times.

Ok, that is clear.
Coming back to wait I said at the beginning I would be really afraid if such a thing exists now since it could disrupt the functioning of everything we rely on nowadays, and as I said, bitcoin would be our last concern.
crazy
copper member
Activity: 1498
Merit: 1528
No I dont escrow anymore.
For easy reference, [7] from the above linked paper can be found here -> https://dl.acm.org/citation.cfm?doid=261342.261346
legendary
Activity: 2142
Merit: 1010
Newbie
Come-from-Beyond,
so let's assume you have a quantum computer that you can use to mine BTC.
Can you use it to disrupt the mining process or not?

Yes, with a QC you can invalidate last 1000 blocks, generate 20000 empty blocks and stop mining leaving the others with 20-year block times.
sr. member
Activity: 574
Merit: 250
In XEM we trust
A quantum computer wouldn't be doing that to a chain using a hash function that uses quantum cryptography, or is that actually your assertion? That quantum computing is a magical panacea?

From http://188.138.57.93/tangle.pdf:

Quote
It is known that a (today still hypothetic) sufficiently large quantum computer can
be very efficient for handling problems where only way to solve it is to guess answers
repeatedly and check them. The process of finding a nonce in order to generate a
Bitcoin block is a good example of such a problem. As of today, in average one must
check around 2^68 nonces to find a suitable hash that allows to generate a block. It
is known (see e.g. [7]) that a quantum computer would need Θ(√N) operations to
solve a problem of the above sort that needs Θ(N) operations on a classical computer.
Therefore, a quantum computer would be around √(2^68) = 2^34 ≈ 17 billion times more
efficient
in Bitcoin mining than a classical one. Also, it is worth noting that if
blockchain does not increase its difficulty in response to increased hashing power,
that would lead to increased rate of orphaned blocks.

Obviously, Bitcoin can't migrate to quantum PoW, miners won't get such hardware in time.
That pdf is a good read, I guess we just have to jump boats to PoS or other protocol before quantum computers hit the mining scene.
But then again how would we secure other protocols if quantum computers could just brute force them?
legendary
Activity: 1176
Merit: 1005
Decentralized Asset Management Platform
Come-from-Beyond,
so let's assume you have a quantum computer that you can use to mine BTC.
Can you use it to disrupt the mining process or not?

I don't understand because before you said that such a computer could
Quote
A quantum computer would rape Bitcoin blockchain with 1000 blocks generated within a minute.

and then quoting that pdf you said
Quote
Obviously, Bitcoin can't migrate to quantum PoW, miners won't get such hardware in time.

So, going back to what I stated at the beginning of this post, if you have a quantum computer could you do that right now or not?

legendary
Activity: 2142
Merit: 1010
Newbie
A quantum computer wouldn't be doing that to a chain using a hash function that uses quantum cryptography, or is that actually your assertion? That quantum computing is a magical panacea?

From http://188.138.57.93/tangle.pdf:

Quote
It is known that a (today still hypothetic) sufficiently large quantum computer can
be very efficient for handling problems where only way to solve it is to guess answers
repeatedly and check them. The process of finding a nonce in order to generate a
Bitcoin block is a good example of such a problem. As of today, in average one must
check around 2^68 nonces to find a suitable hash that allows to generate a block. It
is known (see e.g. [7]) that a quantum computer would need Θ(√N) operations to
solve a problem of the above sort that needs Θ(N) operations on a classical computer.
Therefore, a quantum computer would be around √(2^68) = 2^34 ≈ 17 billion times more
efficient
in Bitcoin mining than a classical one. Also, it is worth noting that if
blockchain does not increase its difficulty in response to increased hashing power,
that would lead to increased rate of orphaned blocks.

Obviously, Bitcoin can't migrate to quantum PoW, miners won't get such hardware in time.
hero member
Activity: 770
Merit: 504
Relevant reading from Koblitz and Menezes: https://eprint.iacr.org/2015/1018.pdf

secp256k1 is a Koblitz curve.

 
 
Oh wow, an actual hardcore mathematician in the wild!  I know I promised not to post anymore until I sobered up, but I would love to hear your opinion on whether moving towards abelian surface cryptography is feasible at all, and whether it would provide any further defense against quantum computers: 
 

My original proposal: https://www.reddit.com/r/math/comments/3451ob/is_it_feasibleworthwhile_to_take_elliptic_curve/ 
 
Shit that's above my head: 
 
http://www.hyperelliptic.org/tanja/conf/ECC08/slides/Peter-Stevenhagen.pdf 
http://research.microsoft.com/pubs/249337/abelian.pdf 
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.464.9485
hero member
Activity: 900
Merit: 1014
advocate of a cryptographic attack on the globe
Relevant reading from Koblitz and Menezes: https://eprint.iacr.org/2015/1018.pdf

secp256k1 is a Koblitz curve.

Abstract. In August 2015 the U.S. National Security Agency (NSA)
released a major policy statement on the need for post-quantum cryptography
(PQC). This announcement will be a great stimulus to the
development, standardization, and commercialization of new quantumsafe
algorithms. However, certain peculiarities in the wording and timing
of the statement have puzzled many people and given rise to much
speculation concerning the NSA, elliptic curve cryptography (ECC), and
quantum-safe cryptography. Our purpose is to attempt to evaluate some
of the theories that have been proposed.

One possibility:

5.5. The NSA has a political need to distance itself from ECC.
There were some peculiarities in the release of the August 2015 statement
about preparing for post-quantum crypto. Normally all of the big corporations
that do cryptographic work for the U.S. government would have been
given some advance notice, but this was not done. Even more surprising,
the NIST people were not asked about it, and even researchers in IAD were
caught by surprise. It seems that whoever at the NSA prepared the release
did so with minimal feedback from experts, and that includes their own
internal experts.

This suggests that the main considerations might not have been technical
at all, but rather Agency-specific — that is, related to the difficult situation
the NSA was in following the Snowden leaks. The loss of trust and credibility
from the scandal about Dual EC DRBG was so great that the NSA might
have anticipated that anything further it said about ECC standards would
be mistrusted. The NSA might have felt that the quickest way to recover
from the blow to its reputation would be to get a “clean slate” by abandoning
its former role as promoters of ECC and moving ahead with the transition
to post-quantum cryptography much earlier than it otherwise would have.
sr. member
Activity: 574
Merit: 250
In XEM we trust
Frist cpu then gpu then asics next quantum computers?

A quantum computer would rape Bitcoin blockchain with 1000 blocks generated within a minute.

If such a technology would exist right now I do think that BTC technology would be the least to be exploited: i.e. imagine what such a mess this quantum computers could create to the entire internet/developed world. There would be nothing secure.
Ok, maybe I'm going too sci-fi now but, yes, I think BTC will be the last thing to worry about
that's an interesting argument, forgot that the bitcoin network is the most secure on the planet at this moment. That means Bye bye every commercial bank on this planet. Bankers should definitely rethink their "secure" systems.
legendary
Activity: 1176
Merit: 1005
Decentralized Asset Management Platform
Frist cpu then gpu then asics next quantum computers?

A quantum computer would rape Bitcoin blockchain with 1000 blocks generated within a minute.

If such a technology would exist right now I do think that BTC technology would be the least to be exploited: i.e. imagine what such a mess this quantum computers could create to the entire internet/developed world. There would be nothing secure.
Ok, maybe I'm going too sci-fi now but, yes, I think BTC will be the last thing to worry about
legendary
Activity: 3430
Merit: 3080
Frist cpu then gpu then asics next quantum computers?

A quantum computer would rape Bitcoin blockchain with 1000 blocks generated within a minute.

A quantum computer wouldn't be doing that to a chain using a hash function that uses quantum cryptography, or is that actually your assertion? That quantum computing is a magical panacea?
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