The problem is not the sha-256 algorithm used for mining but the ECDSA algorithm used for the public-key scheme.

With a quantum computer I could break your private key and steal your money.

Please see this thread:

http://forum.bitcoin.org/index.php?topic=3008.20

Then I think that we should do this ASAP.

quantum computers are a reality, you can buy a 128qubit one for "only" 10$ million (that's small change for a large company)

http://venturebeat.com/2011/05/27/first-quantum-computer-sold/
http://www.dwavesys.com/en/products-services.html


How difficult would be change the algorithm of the public-key encryption for Bitcoin to one not vulnerable to quantum attacks?
Would we have to start from scratch or we could change the algorithm "on the fly" without losing our coins?

Hello,

I have looking at the source code in the function CreateNewBlock() trying to answer myself but I am unable to understand it, looks quite complicated, so I hope anyone can answer my doubts.


How bitcoin chooses the new blocks to calculate the hashes?.

it generates a random block of data and calculate the hash without taking into account if this block was previously calculated in the past?

or it generates a random block and checks if this block was never calculated before calculating the hash for it?

If I turn off my computer, could be bitcoin tomorrow calculating the same blocks than today?


Thanks!