[BIP Proposal] Utreexo Nodes

[Calvin Kim]

Hello all,

Tadge Dryja, Davidson Souza, and I would like to propose 3 BIPs describing Utreexo, a consensus-compatible (non-soft fork) way to send and verify transactions without storing the full UTXO set.

The 3 BIPs are for:

1. The specification of the Utreexo accumulator.
2. The specification of Bitcoin block and tx validation using the Utreexo accumulator.
3. The peer to peer networking changes required to enable Utreexo nodes.

We are currently looking for conceptual review. Do note that the documents are not final, and they will be updated.

All of the BIPs can be found here: https://github.com/utreexo/biptreexo

We thank you in advance for your time and consideration.

Best,
Calvin

[Javier Mateos]

Hi Calvin, Tadge, Davidson,

Thanks for sharing this important work ...it's exciting to see Utreexo maturing into a full BIP proposal. The modular split into accumulator, validation, and P2P layers is very clean and helpful for review.

After a quick conceptual and implementation-level analysis, I believe there's a critical detail missing from the current accumulator spec: a deterministic order for processing UTXO deletions and additions per block.

Aside from that, the spec is well written and shows deep consideration.

Best regards,

[K Calvin]

Hey Javier,

Thanks for taking the time to do the conceptual analysis.

As for the missing detail you mentioned, I think this section in the validation BIP has that covered:

https://github.com/utreexo/biptreexo/blob/main/utreexo-validation-bip.md#order-of-operations

We wanted the accumulator BIP free from any Bitcoin related operations. Thus anything that has to do with validation of Bitcoin blocks will be found in the validation BIP.

Best,

Calvin

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[Murch]

Hello Calvin and all,

Thank you for sharing your drafts. I skimmed your proposals and found
them to be shaping up nicely. I didn’t notice anything worth conceptual
feedback at this time, but will have plenty comments later in the
process when they are more fitting. Obviously, utreexo has had a lot of
discussion in the past already and these proposals are fairly close to
the editorial requirements, so please feel free to open pull requests
for the proposals whenever you feel ready to do so.

Cheers,
Murch

On 2025-07-29 16:20, Calvin Kim wrote:
> Hello all,
>
> Tadge Dryja, Davidson Souza, and I would like to propose 3 BIPs
> describing Utreexo, a consensus-compatible (non-soft fork) way to send
> and verify transactions without storing the full UTXO set.
>
> The 3 BIPs are for:
>

> 1. The specification of the Utreexo accumulator.
> 2. The specification of Bitcoin block and tx validation using the
> Utreexo accumulator.
> 3. The peer to peer networking changes required to enable Utreexo nodes.

>
>
> We are currently looking for conceptual review. Do note that the
> documents are not final, and they will be updated.
>
> All of the BIPs can be found here: https://github.com/utreexo/biptreexo
>
> We thank you in advance for your time and consideration.
>
> Best,
> Calvin

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> To unsubscribe from this group and stop receiving emails from it, send
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[Calvin Kim]

Hello Murch,

Thank you for the review and the PR is now made at https://github.com/bitcoin/bips/pull/1923

Best,

Calvin