David A. Harding [ARCHIVE] on Nostr: 📅 Original date posted:2019-11-14 📝 Original message: On Thu, Nov 14, 2019 at ...

📅 Original date posted:2019-11-14
📝 Original message:
On Thu, Nov 14, 2019 at 10:56:05AM +0100, Joost Jager wrote:
> Looking at https://github.com/bitcoin/bitcoin/commit/9022aa3, is
> `dustRelayFee` really never going to change? It even is a (hidden) cmd line
> parameter that can be set easily.
>
> If the fee market would rise and stay high for an extended period of time,
> why wouldn't people use this flag to raise the dust relay fee?

If feerates are reliably high, then there's less need for the dust limit
and I wouldn't expect it to be increased.

The dust limit exists to prevent people from filling the UTXO set with
non-economical UTXOs when feerates are low. For example, at the current
minimum relay fee of 1 sat/vbyte and price of $8,500 USD/BTC, the cost
to create a zero-value[1] P2WPKH output is about 30 vbytes = 30 sat =
$0.0025 (1/4 cent). The current UTXO set has about 64 million entries,
so the cost to double its size would be $160,000---a tidy sum, but
probably less than some people spend spreading anti-Bitcoin propaganda
on a regular basis.

The dust limit helps prevent that by making the minimum cost per created
P2WPKH UTXO 30 sat + 294 sat = $0.0275, or about $1,760,000 per UTXO set
doubling.

If feerates increase, the cost of a UTXO-filling attack rises
proportionally. Somewhere around sustained minimum feerates of 11
sat/vbyte, feerates alone become more expensive than the current level
of protection provided by the dust limit at 1 sat/vbyte.

Additionally, it's worth noting that the dust limit is not
incentive-aligned with short-term miner interests. If there's actual
legitimate demand to create transactions paying reasonable feerates and
containing uneconomical-to-spend outputs, then miners are going to start
accepting those transactions no matter what policies are implemented on
the P2P transaction relay network.

In short, I don't expect dust limits to rise unless the BTC/fiat price
drops so far that UTXO-filling attacks become much more affordable than
they are with today's limits. Dust limits may instead decrease (or be
removed), but I don't think that's a problem for anchor outputs.

That said, I think it'd be a nice thing for LN implementations to strive
to create anchor outputs that are economical to spend and that may
require using a negotiable output amount to compensate for rises in
feerates making small-value outputs less economical, especially if
you're using different anchor outputs for each channel party.

-Dave

[1] I believe consensus rules allow creating zero-value outputs. If
not, making this a 1 sat output doesn't significantly change any
calculations.

P.S. Perhaps see also Gregory Maxwell's take:

> I suspect that if feerates hadn't tanked after the introduction of
> segwit, implementations probably would have removed the dust limit
> policy rules in any case: they're a kludge that compensates for fees
> being too low to dissuade various antisocial behaviors like spamming
> for advertising purposes or de-anonymizing users and don't serve much
> purpose if feerates are consistently high enough to discourage these
> attacks.

Source: https://bitcoin.stackexchange.com/a/85696/21052