on sha256 security bit are only 128, and quantum computer can break this(i can't find the article), if today pc can break 64 quantum computer can break at least the double of that
so bitcoin will need an hard fork in the future to survive
Stop talking nonsense. Quantum computers can't break SHA256 (used for hashing) without brute forcing it unless a flaw in it has been found. There is no article to link. I'm not saying that someone won't find a way to attack it in the future though.
you are wrong it can break 128 key(the power of quantum computer is like a pc that halve the difficulty, and if today pc, tons of them, could break 64, then a quantum can break 128) this is not enough to break sha256(or the private key which is 256 bit)
i know, i didn't explain it well, but it is enough to break the pubblic key which is 128 bit
Your English levels are under those of a 5th grader. Consider taking a course, because you complicate things and usually make no sense.
I never said that SHA256 for a normal computer wasn't SHA128 for a quantum one. You didn't explain it because it can't be explained well i.e. what you said effectively makes no sense. A quantum computer can't beat SHA 256 (i.e. SHA 128). Actually if SHA gets broken the problem will be on a much larger scale where Bitcoin will be irrelevant (unless globally adopted). A lot of things use SHA, for example banks.
What I'm trying to say is: For SHA256, it effectively becomes SHA128 to a Quantum computer. Now the question remains, can a Quantum search for SHA128 faster than a classical computer search through SHA256?
With out current technology and for the near future, we still can't build a real Quantum computer that can even begin to tackle this problem, let alone solve it.
i think you are not understanding, my english was clear enough in the last post you quoted, quantum computer can break any 128 key, it has been said many times, there is no question here
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-bitcointhere are many other confirming this
Thank you to this link, thanks to it I have found this thread (of Come-from-Beyond) :
As we all know elliptic curve cryptography is vulnerable to a quantum computer. For a conventional computer difficulty of breaking 256-bit key equals 256/2=128 bits. For a quantum computer it's just sqrt(256)=16 bits.
Bitcoin address is a hashed public key of 256-bit EC. Hashes are resistant to quantum algos, so while someone keeps his public key unknown it's OK. But when he wants to transfer his money he must reveal the key.
Let's assume that an attacker with a quantum computer monitors all transactions. The attacker can pick any key while a transaction awaits to be included into a block. Now imagine that miners choose transactions with higher fees. The attacker can issue other transaction (when he picks the private key) that transfer coins to his address and set a higher fee. Or he could switch his mining rig on and try to find a block himself. With 0.1% of all hashpower he needs only 5 days to solve a block with 50% chance.
Seems Bitcoin is NOT safe. Or am I wrong?
We can assume everything because I didn't still see a valid and functionally quantum computer.