Quote from: robot_boy on January 26, 2013, 11:16:50 PM

Well, that is both some what worrisome and somewhat reassuring to hear. One of my concerns was that people are not always great about backing up their files and if enough people fail to back up the wallets and their computer goes down you may end up with a great deal of money just sitting around outside of the system because they can no longer get to it. The ability to at some point in the future bring that money back into circulation seems like it could get rid of that problem. The part that worries me is that those same people could also get into active wallets and take money that was not lost. I may be horribly misunderstanding something and be horribly off base with this statement. I am new to this and have only seen a few videos and what not, so I am no expert.

It is nothing to worry about. Today performing a brute force attack on a 256 bit key is simply impossible. It won't become possible without breakthroughs in physics that give us access to energy on a scale the human race has never seen before. Just counting from 0 to 2^256 would require more energy than our star has left (yes the entire lifetime output of our sun).

The only theoretic scenario where addresses could be attacked is that on a very long timeline (potentially decades or centuries) the cryptographic algorithms which make up Bitcoin could be compromised allowing a faster than brute force attack. Generally these types of attacks take years if not decades to develop from an academic paper to something which can be done in the real world. That would give active users plenty of time to move funds to "new" (as of yet not invented) address types based on stronger cryptography. Long before any such attack could be made the only coins left in vulnerable addresses would be the ones that couldn't be moved because the private keys have been long since lost.