Re: [bitcoin-dev] UHS: Full-node security without maintaining a full UTXO set

[Cory Fields <lists@coryfields.com>]

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Matt: That's a good point. I'll do up a chart comparing utxo size at each
block, as well as comparing over-the-wire size for each block. I think the
period of coalescing earlier this year should be a good example of what
you're describing.

Greg: heh, I was wondering how long it would take for someone to point out
that I'm cheating. I avoided using the word "compression", mostly to
side-step having the discussion turning into reworking the wire
serialization. But you're absolutely right, the de-duping benefits are
independent of the UHS use-case.

Cory

On Thu, May 17, 2018, 12:56 PM Gregory Maxwell <greg@xiph.org> wrote:

> On Wed, May 16, 2018 at 4:36 PM, Cory Fields via bitcoin-dev
> <bitcoin-dev@lists.linuxfoundation.org> wrote:
> > Tl;dr: Rather than storing all unspent outputs, store their hashes.
>
> My initial thoughts are it's not _completely_ obvious to me that a 5%
> ongoing bandwidth increase is actually a win to get something like a
> 40% reduction in the size of a pruned node (and less than a 1%
> reduction in an archive node) primarily because I've not seen size of
> a pruned node cited as a usage limiting factor basically anywhere. I
> would assume it is a win but wouldn't be shocked to see a careful
> analysis that concluded it wasn't.
>
> But perhaps more interestingly, I think the overhead is not really 5%,
> but it's 5% measured in the context of the phenomenally inefficient tx
> mechanisms ( https://bitcointalk.org/index.php?topic=1377345.0 ).
> Napkin math on the size of a txn alone tells me it's more like a 25%
> increase if you just consider size of tx vs size of
> tx+scriptpubkeys,amounts.  If I'm not missing something there, I think
> that would get in into a very clear not-win range.
>
> On the positive side is that it doesn't change the blockchain
> datastructure, so it's something implementations could do without
> marrying the network to it forever.
>

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