On Mon, Sep 28, 2015 at 04:33:23PM +0200, Mike Hearn wrote:
> >
> > SPV wallets can't detect hard-forks
> 
> 
> They don't have to - they pick the highest work chain. Any miner who hasn't
> upgraded makes blocks on the shorter chain that are then ignored (or
> rather, stored for future reorgs). After the fork point, there won't be any
> blocks in the main chain that violate the rules and end up being doomed to
> being orphaned, which is the underlying problem.
> 
> And I think you know this already. There is no "flaw" in bitcoinj in this
> respect. It works exactly as it was designed to work.

Ok, so again, if that's your security criteria, what's the issue with
soft-forks? With soft-forks, the result of a SPV wallet following the
highest work chain is the same: eventually invalid blocks are reorged
out.

However, because soft-forks make it less likely that a long invalid
chain will be generated, an attacker sybil attacking your SPV wallet has
a much harder time tricking it into accepting a transaction. (they might
get one or two confirmations, rather than dozens)

What's the scenario where soft-forks are worse than hard-forks from a
SPV wallet's perspective?

-- 
'peter'[:-1]@petertodd.org
00000000000000000368227ec1de9c27c14d23cb7be9e9f38c0082db79a87c49