Subject: Re: [Bitcoin-development] Auto-generated miner backbone

From: Mike Hearn <[email-masked]>
Date: Mon, 4 Nov 2013 16:27:58 +0100

On Mon, Nov 4, 2013 at 3:26 PM, Peter Todd <[email-masked]> wrote:

> The attacker now only needs to connect to every identified miner
> with especially fast nodes. With judicious use of DoS attacks and low
> latency .....
>

So you're back to a complicated sybil attack. I don't follow your thought
process here - I didn't say anything about numerical advantage. The attack
outlined in the paper *requires* you to be able to race the rest of the
network and win some non-trivial fraction of the time. If you can't do that
then all it means is that when you try to release a private block to
compete with the other found block, you're quite likely to lose and you
sacrifice the block rewards by doing so.

> The correct, and rational, approach for a miner is to always mine to
> extend the block that the majority of hashing power is trying to extend.
>

There's no stable way to know that. The whole purpose of the block chain to
establish the majority. I think your near-miss headers solution is
circular/unstable for that reason, it's essentially a recursive solution.

> Mining strategy is now to mine to extend the first block you see, on the
> assumption that the earlier one probably propagated to a large portion
> of the total hashing power. But as you receive "near-blocks" that are
> under the PoW target, use them to estimate the hashing power on each
> fork, and if it looks like you are not on the majority side, switch.
>

But you can't reliably estimate that. You can't even reliably estimate the
speed of the overall network especially not on a short term basis like a
block interval.