On Fri, Jun 13, 2014 at 10:43 PM, Perry E. Metzger wrote:

And how do these others know that the public key in question has any connection to a particular set of coins in the ledger? How do they know that some other key, in fact, isn't the correct one?

Because the former owner signed the 'coins' over to the public key in question, confirmed all the way back to their first generation, in a ledger back to the genesis. You were given (bought) the deed of your house from someone, confirmed by many titles before in recorders ledger, right?

Who is everybody?

Everyone who says, "well, my chain was at this height before suspect 51% attack (or other) issue, let's compare." Though that's an event you *really* want to avoid. Thus for their own good people will move off ghash.io. Or will plain stop transacting and starve the pools of trans fees and trans to scam. And how many dollars on hardware and power would an 'unknown' pool of say government or criminals need to reach 51% on their own for disruption or profit? By now, maybe an amount that might be hard to keep quiet.

Do millions of people actually store and check the complete block chain on a routine basis? Where did your little cellphone wallet app get its blockchain from? When was the last time you verified the custody chain of all coins? Does your cellphone wallet app do that all the time? Where do people get this historical ledger from?

There are verifiable and agreed upon checkpoints... https://en.bitcoin.it/wiki/Checkpoint_Lockin https://bitcointalk.org/index.php?topic=145386.0 https://bitcointalk.org/index.php?topic=117982.0 https://bitcointalk.org/index.php?topic=252937.0

I think you're trusting quite a bit here.

Bitcoin isn't primarily protected by mathematics, it is primarily protected by a social process that can be gamed. Gaming it is nontrivial because the social process is protected by cryptography, but there seems like a great deal of religion behind people's claims of how well it all works in the face of attack, perhaps because a lot of people want it to work very, very badly.

Agreed there is a lot of trust, crazy trust, and the adoption in actual business using it (not simply user2user beer and pizza trade), is a bit amazing. So far it's held up. Try to break it or game it, mathematically or operationally, huge recognition for anyone who does. Those with personal money (not mined) in their hoards are on their own risk decision on that, at least until say the ten year mark and the laws prove out. Others have mined or can mine, or invest, to recover/recoup their entry which makes it free for them. The rest seem to get in, buy a pizza, and get out (perhaps wisely). https://en.bitcoin.it/wiki/Contingency_plans Lots people should read, learn and evaluate, me too. Meanwhile, I don't have a problem putting some disposable funds into holding, trading, commerce, or related bitcoin business and seeing what happens. Call me stupid, seems more fun, profitable and useable than blowing lottery tickets would be. And if that's all it's ever good for you can have my wallet after you break Bitcoin ;-) https://en.bitcoin.it/wiki/Trade https://bitcoinaverage.com/