Quote from: Hexadecibel on August 23, 2013, 07:00:45 PM

Very interesting what you've put together.

When these sorts of posts pop up I like to point people to a blog post by Gavin, the lead developer of the core bitcoin software:

http://gavintech.blogspot.com/2012/05/neutralizing-51-attack.html

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One of the things a 51% attacker can do is prevent any transactions or new blocks from anybody besides themselves from being accepted, effectively stopping all payments and shutting down the network.

That would be bad.

But it would also be obvious it was happening, and pretty easy to defend against. As I said on the Bitcoin Forums:

Something like "ignore a longer chain orphaning the current best chain if the sum(priorities of transactions included in new chain) is much less than sum(priorities of transactions in the part of the current best chain that would be orphaned)" would mean a 51% attacker would have to have both lots of hashing power AND lots of old, high-priority bitcoins to keep up a transaction-denial-of-service attack. And they'd pretty quickly run out of old, high-priority bitcoins and would be forced to either include other people's transactions or have their chain rejected.

So not only is the price tag to attack the network ever increasing, there is also the fact that if 'X' organization spends the millions of dollars to attack bitcoin, they risk it merely being circumvented. Thats a lot of wasted money, a lot to answer for if you fail.

You are 100% correct, there are other problems needed to successfully pull off a 51% attack. We hope our model offers insight, however. Especially over time.