elip201: Reduce Elements default dust relay feerate to match min relay feerate

[kilrau]

No description provided.

[delta1]

Hi @kilrau, thanks for the submission.

As you note, the "dust limit" for output types is node policy and unrelated to consensus of the network.

The default dustrelayfee rate is 3 sats/vb (3000 sats/kvb) 1.

This only becomes an issue with certain Elements RPCs. As you demonstrated a wallet can trivially create confidential outputs with lower amounts.

In my testing, a confidential WPKH output has a base size of 98 bytes. The function GetDustThreshold then adds a further 67.75 bytes, giving a floored total of 165 bytes. At the default dustrelayfee of 3 sat/vb this gives a dust threshold of 495 sats.

By reducing the dustrelayfee on your node to 0.1 sats/vb (100 sats/kvb), your Elements RPCs can create confidential WPKH outputs with amounts as low as 17 sats ( 165 vb * 0.1 sats/vb rounded up to the next int ).

There is an IsDust check in IsStandardTx 2, but this can only be checked for explicit transactions.

I am not sure this requires an ELIP, personally I'd be happy to accept a PR to Elements reducing the DUST_RELAY_TX_FEE to match the DEFAULT_MIN_RELAY_TX_FEE of 0.1 sats/vb (100 sats/kvb) 3. But if we do want to keep this information in an ELIP then I think it just needs similar motivation as above and titled something like "Reduce default dust relay fee in Elements".

[delta1]

@apoelstra what do you think?

[kilrau]

Originally I was tasked to create this ELIP to "have something tangible to track" for the effort to lower the dust limit across the Liquid wallet ecosystem. But I am fine to reduce this to be applicable to Elements-only as proposed by @delta1 or even just close it as in that case prbly all it takes is ElementsProject/elements#1433

[delta1]

Updated as per the discussion and reference PR

ACK 4be5ce4

[psgreco]

ACK 4be5ce4