Hi Insiders. This is Tuma, open-source reporter from the Insider Edition.

In this week’s update we feature current effort to add support for recurring payments with BOLT12 in LDK.

We also cover the announcement of two new offchain protocols on Bitcoin, namely Zark by Lx DEV, a statechain with a blinded co-signer and zero-knowledge proofs, and LayerTree by Lightning Labs, a non-custodial scaling solution which allows multiple users to share a Bitcoin UTXO.

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Highlights from the Bitcoin developer ecosystem

I spent 10+ hours in open-source developer calls in the Bitcoin ecosystem last week. Here is what caught my eye:

• LDK contributors are working on adding support for BOLT12 recurrence in the Lightning Implementation.
  • During the biweekly call, on Monday 12th, LDK contributors discussed the latest updates to the Lightning implementation. One of the most interesting things devs are working on right now is adding support BOLT12 recurrence in LDK Node.
  • Developer Shashwat Vangani is currently working on PR1119 in LDK Node, which builds on the previous work done in rust-lightning — which introduced protocol primitives, message handling, and payment flow.
  • This PR introduces the management whole recurrent payment workflow to LDK Node, such as persistence of recurrent payment state, updates, scheduling, and APIs for applications to manage recurrence.

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A BIPs Update

There was no newsworthy update in the last days in the BIP repository. We’ll provide new updates as soon as a new BIP gets published or gets assigned a number.

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Other News from the Bitcoin World

• Zark: Lx Dev announced a new protocol for private, offchain Bitcoin transfers called Zark. The protocol is based on the statechain paradigm and leverages zero-knowledge proofs to improve users’ privacy.

  • The protocol’s coordination relies on a co-signer. This entity is blinded, which means that it signs a UTXO transfer without getting to know the specific details about the transfer itself. Users need to trust the co-signer to delete the keyshares belonging to a previous owner.
  • Users can prove their ability to spend, receive, and withdraw coins using zero-knowledge proof. This means that inside the protocol the amount of leaked information about previous owners — such as payout addresses — is highly reduced, improving privacy.
  • Lx Dev published an extensive overview of Zark, which dives into how the protocol works and which are the trade-offs to be taken into account.

• LayerTree: Lightning Labs announced LayerTree, a new non-custodial scaling solution on Bitcoin, which allows multiple users to share a Bitcoin UTXO.

  • Ownership is recorded offchain into a Merkle-sum tree in which each leaf represent a user’s balance, and Each node of the tree holds a hash of its children, up to the root. The shared UTXO commits to the root of this tree.
  • The protocol cannot work on Bitcoin as it is today. According to Lightning Labs CTO Olaoluwa Osuntokun, LayerTree needs covenant to work. Interestingly enough, no specific opcode is needed, but the protocol could work with any of the proposals already drafted.
  • Lightning Labs published a full website, which allows users to interactively understand how the protocol works.

• Post-quantum Shielded CSV: Jonas Nick reported that a research group from Imperial College had published a paper introducing a post-quantum version of ShieldedCSV, called Compact ShieldedCSV. Unlike ShieldedCSV — where the nullifier carries a signature — Compact’s nullifiers carry no signature, only something called a “degriefer”.

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More from BTC++ Insider Edition

News Hour#

• BTC++ News Hour: Check out our Friday livestream, where Matthew Vuk and I discuss the most interesting news of the week from the Bitcoin developer ecosystem. This time, we hosted our first guest, Lx Dev CEO Janusz, to talk about Zark.

Videos#

• Pim Keer — BTC++ Insider Interviews: Pim Kerr, PhD Researcher at the Security and Privacy Group of TU Wien, talks to the Insider about the work his research group is doing to formalize and prove the security of the Ark protocol.
• Pietro Valese — BTC++ Insider Interviews: Pietro Valese, Lab Manager at BitPolito, talks to the Insider about what BitPolito is and what it is doing to connect students and the Bitcoin industry.
• TheMhv — BTC++ Insider Interviews: TheMhv, Vinteum fellow and Cashu contributor talks to the insider about his work on the Cashu Development Kit (CDK), new NUTs, and the importance of meeting the people you work with in real life.

Articles#

• The prefill was already there - This Week in Bitcoin Core #62

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Looking for an opportunity to join up with some bitcoin devs in person? Join us in Seoul this November 5-6 to talk about privacy in Bitcoin!