On Wed, May 13, 2015 at 12:31 PM, Alex Mizrahi <alex.mizr...@gmail.com> wrote: > But this matters if a new node has access to the globally strongest chain. > If attacker is able to block connections to legitimate nodes, a new node > will happily accept attacker's chain.
If you get isolated from the network you may not get the longest valid chain. I don't think any other consensus mechanism deals with this better than Bitcoin. > So PoW, by itself, doesn't give strong security guarantees. This problem is > so fundamental people avoid talking about it. > > In practice, Bitcoin already embraces "weak subjectivity" e.g. in form of > checkpoints embedded into the source code. So it's hard to take PoW purists > seriously. Checkpoints are NOT part of the consensus rules, they're just an optimization that can be removed. Try keeping the genesis block as your only checkpoint and rebuild: it will work. You can also define your own checkpoints, there's no need for everyone to use the same ones. In a future with committed utxo the optimization could be bigger, but still, we shouldn't rely on checkpoints for consensus, they're just an optimization and you should only trust checkpoints that are buried in the chain. Trusting a committed utxo checkpoint from 2 years ago doesn't seem very risky. If the code is not already done (not really sure if it was done as part of auto-prune), we should be prepared for reorgs that invalidate checkpoints. So, no, Bitcoin does NOT rely on that "weak subjectivity" thing. ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Bitcoin-development mailing list Bitcoin-development@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/bitcoin-development
