Topic: Quantum Computer vs Bitcoin - page 7. (Read 2502 times)

It's something that Bitcoin's designers need to keep in mind as a "tail risk".

Quantum computers reduce the effective security of our strongest cryptographic primitives (hashes, symmetric ciphers) by about half. That is, a 256-bit hash gives about 128 bits of effective security in a world where quantum computers are used for at-scale computation. 128 bits of security is pretty good security - searching 10³⁷ gives about a 10% chance of breaking a particular hash (finding the hash preimage). 10³⁷ is 10 quadrillion quadrillion quadrillion - that's more than a billion billion times the number of hashes performed by the combined hashpower of all Bitcoin miners in order to mine a block.

The hash address is only 160 bits but it still requires 256 bits of search to break, that is, address=RIPEMD160(SHA256(pubkey)) minus a few technical details. Once you get the pubkey, we typically assume that a quantum computer will easily recover the private key from the public key. However, quantum-resistant public key encryption is still possible. Because of its quadratic advantage (theoretical) over classical computers, we have to double the key space (note that this may more than double key size). IIRC, secp256k1 is 128-bits equivalent security which we have to cut in half in a quantum-computation world - effective security is 64-bits. While 64-bits is too small for securing a large asset (such as all bitcoins), note that each address is secured by 64-bits security. So the cost of breaking all addresses in the UTXO set is at least 64 * nUTXO where nUTXO is the number of unspent transaction outputs. In other words, even with a quantum computer, you still have to break each address separately, and there are a lot of addresses.

Finally, quantum computation will actually help Bitcoin more than it will hurt it. As QC's begin to approach sufficient complexity to be able to mount serious attack against Bitcoin's cryptographic primitives, they are going to force cryptographers to revise usage across many cryptographic applications - traditional banking, government communication and data-storage, military communications systems, and so on. Quantum cryptography offers the promise of new modes of communication that are not possible with classical communication channels. Perhaps you can secure your Bitcoin address with an entangled set of qubits such that only the holder of the originally entangled qubits can prove ownership of the address. So, Bitcoin should not be having FUD about QC.

No.  The fear is that if could do something like get a private key from a public key, but the hash function should mitigate that risk unless you are reusing addresses.

You could spin up 10000 nodes right now pretty easily.

My main hope is that quantum computers revolutionize search since this has been discussed many times before. 😂

Quantum computer is already existing but none of the issue that bitcoin will be destroyed by any super what kind is it done it. Creator can only destroy bitcoin. Nodes,block,codes etc. If this is copied in the original of it then it might happen. But the question is why going to destroy bitcoin if youll be able to use it and become millionaire.

I'm probably wrong but here's my opinion on the subject. Others please feel free to correct me if I say something false.

So the whole structure of bitcoin is based on a p2p (peer to peer) network. Each wallet (full node) and miner that is has a copy of the blockchain verify the activity. The vulnerability that comes to mind when I think of a crazy super quantum computer's ability to attack bitcoin is this; what if the computer was able to create enough of it's own nodes to control over half of the network? Hopefully someone with more knowledge will elaborate on this. Because I don't think I understand how bitcoin works fully.

and i heard too that quantum computer can destroy bitcoin system is just a myth

Yes and no.

Efficient quantum computer can get the private key from public key, which means it could empty wallets that have been spend from. A single send action from an address reveals the public key.

However. If you use bitcoin properly and do not re-use addresses, then you are safe from quantum computers, because they cannot break SHA256 hash.

Also if/when quantum computers would ever become big enough, bitcoins encryption is probably going to be changed to something quantum resistant.

How do we know when the time has come?
There are several addresses with over 1000000000$:s worth of bitcoins in them, that have send actions in them and they have published their public keys. When someone starts emptying them, then we know it is time to do something.... or hopefully long before that.

And it is not only quantum "magic" computers we need to worry. Maye someday some hacker will find a way to break bitcoin crypto even without quantum magic.

Yes.

The word "quantum" is a synonym for "magic".  A quantum computer is a magic computer that can do anything you want it to do as fast as you want it to do it.


There is no reason to think that a quantum computer will destroy bitcoin.  Extraordinary claims require extraordinary evidence.

I heard that Quantum Computer can destroy bitcoin.
Is it possible?