Quote from: Amph on April 16, 2015, 07:47:07 PM

Quote from: LaudaM on April 16, 2015, 06:10:49 PM

Quote from: Amph on April 16, 2015, 01:53:57 PM

now, public key are 128 bit, instead private key are 256, so the first can be brute forced by any quantum computer, and if you have that key you could retrieve the private key, but this only if the targeted public key is send when you spend a transaction

here a link http://bitcoin.stackexchange.com/questions/6062/what-effects-would-a-scalable-quantum-computer-have-on-bitcoin

there are many other confirming this

To summarize: You're wrong. Existing implementations have not shown that they can beat 128bit encryption. They aren't even close. That's the current situation. I'm not saying that in 5 years we won't have better technology. We might operate with 1400 qubits or be stuck at 140. Nobody really knows.

there are many quote that say otherwise, so no i'm not wrong at all, for a quantum computer brute-forcing a 256 key is like for a normal computer brute-forcing 128 key, it's like dividing by two(the exponent not the number, so is equal to a root square of it), this should be clear, and with that in mind you could deduce easily, that a 128 key for a quantum computer is equal to a 64 key for a modern computer, and a 64 key can be brute-forced with a normal computer(not just one i know, but a very big farm can do it)

just simple logic, you don't need to search for anything to deduce this...

Your logic is severly flawed.

Quote from: Amph on April 16, 2015, 01:53:57 PM

-snip-
here a link http://bitcoin.stackexchange.com/questions/6062/what-effects-would-a-scalable-quantum-computer-have-on-bitcoin
-snip-

Click on your link, click on the link back to bitcointalk.org, read the post by danny.

Quote from: DannyHamilton on December 26, 2012, 10:06:56 PM

-snip-

Quote from: furrycoat on December 26, 2012, 10:01:04 PM

. . . will Quantum computing destroy Bitcoin? . . .

No.

http://lmgtfy.com/?q=quantum+site%3Abitcointalk.org

Need a bit more?

Quote from: etotheipi on December 28, 2012, 04:11:57 AM

Quote from: imanikin on December 26, 2012, 11:23:59 PM

This should be in all stickys and faq's! Seems like every week lately we have a thread on this same old topic. I know the search engine is very bad on this forum, but i think most of the noisemakers are just too lazy to even use it.

I think at least this video from the summit should be compulsory to watch before being able to post on this forum.

...except that the speaker got the question about quantum computing wrong. I was in the audience, but I was too much of a pussy to stand up and correct him in front of everyone. Apparently, I should have done so (since he has now been cited by someone), but I'm shy like that -- especially because I was in the back and no one had any idea who I was. Oh well.

The speaker says that ECDSA is not susceptible to QCs -- that's just wrong. ECDSA is most definitely broken by QC's, as well as just most asymmetric crypto algorithms on which internet security relies. But Bitcoin is better prepared to deal with QCs than most other crypto systems: (1) if you never reuse addresses, then no one knows your public keys and thus there's nothing for a QC to solve. By the time someone gets your public keys, you've already spent the funds, (2) the crypto algorithms in Bitcoin can be changed to quantum-resistant ones. Given that we'll probably have two decades advance notice before QCs with enough qubits exist to even threaten Bitcoin, we'll have plenty of time to make the switch.

Quote from: DooMAD on April 16, 2015, 08:59:15 PM

Quote from: bennybong on April 16, 2015, 08:03:34 PM

+1 to whoever posts that picture explaining about how the laws of thermodynamics would have to be broken to crack SHA256...

The original one was posted here and probably a few dozen other places as well. I thought the background looked a little dull, so I made my own version.

Maybe you could fix the errors in it, because we dont need to "count" to 2²⁵⁶ we need to "count" to 2¹⁶⁰ due the use of RIPEMD 160