UTXO commitments may be needed if blocks get very large as BCH gains popularity and adoption. Calin starts by explaining UTXOs (unspent transaction outputs) and the basic data fields every UTXO contains.

He then describes UTXO commitments, the changes required to introduce them, and the advantages and risks involved in going forward with UTXO commitments.

Calin Culianu is a prolific BCH developer, and maintainer of many things such as BCHN, Fulcrum Server, and Electron Cash wallet.

Links:

Calin Culianu on Twitter: https://x.com/cculianu

Bitcoin Verde UTXO Fastsync proposal: https://bitcoincashresearch.org/t/chip-2021-07-utxo-fastsync/502

SLIDES: https://docs.google.com/presentation/d/1-kJhYnbh89ytfldnykbxpfyiDVqsA2zi47byyX1eujU/edit?usp=sharing

Donations:

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Sponsors:

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Also by: Mike Komaransky, Molecular, Toorik, Mini-Satoshi

Socials:

Website: https://www.bitcoincashpodcast.com

Timestamps:

0:00 Intro

01:00 s/o to Josh Green & Andrew Groot @ Bitcoin Verde

01:26 What is a UTXO

01:58 UTXO life cycle and state

04:00 UTXO sets

04:12 Why is the UTXO set important?

04:56 Why do nodes need blocks?

05:34 Is IBD from 0 a problem?

06:06 Why not just download UTXO set?

06:44 BCH unchained!

07:50 UTXO commitments

08:58 Minimal download

09:36 Trade-offs vs. Initial Block Download (IBD)

10:51 UTXO commitments is an old idea

11:53 "UTREEXO"

13:19 "Flat" UTXO table

14:37 "Flat" set challenges

15:42 Elliptic Curve Multiset Hash (ECMH)

16:31 ECMH overview

17:28 ECMH properties

18:47 Bucketing for scale

19:20 UTXO commitments

20:05 Consensus changes

20:36 P2P protocol changes

21:13 Initial phase-in

22:21 Activation on-chain

22:47 Advantages of UTXO commitments

23:41 Risks

24:29 Links for further reading

24:50 Q : UTXO snapshots

26:09 Q : Mempool synchronization

27:42 Q : Joining hashes

28:44 Q : Orphan blocks

29:21 Q : History of EC hash function

30:05 Q : Mempool

31:49 Q : Coin base transaction

32:35 Q : Assessing risks

34:26 Outro

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