[bitcoin-dev] Capacity increases for the Bitcoin system.

Jonathan Toomim j at toom.im
Wed Dec 9 00:40:46 UTC 2015

On Dec 9, 2015, at 8:09 AM, Gregory Maxwell <gmaxwell at gmail.com> wrote:

> On Tue, Dec 8, 2015 at 11:48 PM, Jonathan Toomim <j at toom.im> wrote:
> By contrast it does not reduce the safety factor for the UTXO set at
> all; which most hold as a much greater concern in general;

I don't agree that "most" hold UTXO as a much greater concern in general. I think that it's a concern that has been addressed less, which means it is a more unsolved concern. But it is not currently a bottleneck on block size. Miners can afford way more RAM than 1 GB, and non-mining full nodes don't need to store the UTXO in memory.I think that at the moment, block propagation time is the bottleneck, not UTXO size. It confuses me that SigWit is being pushed as a short-term fix to the capacity issue when it does not address the short-term bottleneck at all.

> and that
> isn't something you can say for a block size increase.


I'd really like to see a grand unified cost metric that includes UTXO expansion. In the mean time, I think miners can use a bit more RAM.

> With respect to witness safety factor; it's only needed in the case of
> strategic or malicious behavior by miners-- both concerns which
> several people promoting large block size increases have not only
> disregarded but portrayed as unrealistic fear-mongering. Are you
> concerned about it?

Some. Much less than e.g. Peter Todd, for example, but when other people see something as a concern that I don't, I try to pay attention to it. I expect Peter wouldn't like the safety factor issue, and I'm surprised he didn't bring it up.

Even if I didn't care about adversarial conditions, it would still interest me to pay attention to the safety factor for political reasons, as it would make subsequent blocksize increases much more difficult. Conspiracy theorists might have a field day with that one...

> In any case-- the other improvements described in
> my post give me reason to believe that risks created by that
> possibility will be addressable.

I'll take a look and try to see which of the worst-case concerns can and cannot be addressed by those improvements.
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