Spark: A New L2 for Bitcoin with Kevin Hurley | SLP700

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Oct 31, 2025

In this engaging discussion, Kevin Hurley, CTO and co-founder of Lightspark, shares his transition from the Libra project to developing Spark, a user-friendly Layer 2 solution for Bitcoin. He highlights the challenges of the Lightning Network, including liquidity issues, and explains how Spark simplifies user experience while ensuring privacy and security. Kevin dives into the unique state chain design, unilateral exits, and the potential for asset tokenization within the Spark ecosystem, emphasizing community involvement and future developments.

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ANECDOTE

From Libra/Diem To Building On Bitcoin

Kevin recounts moving from Meta's Libra/Diem effort to building on Bitcoin because of neutrality and decentralization concerns.
He explains Lightspark first built Lightning tooling (Connect) then pivoted to design Spark after recurring Lightning scaling pain points.

INSIGHT

Lightning Suits Custodial Use; Spark Targets Self-Custody

Lightning scales well for custodial, B2B use but struggles for billion-user self-custody due to inbound liquidity and capital inefficiency.
Spark targets self-custody at scale by sharing liquidity, supporting stablecoins, and enabling unilateral exits.

INSIGHT

Key-Tweak State Model With Tree-Structured Leaves

Spark uses a statechain-like key-tweaking model where operators adjust keys and forget old material to transfer ownership off-chain.
Lightspark modified classic statechains with a tree of pre-signed leaves to remove absolute time bombs and support arbitrary denominations and re-aggregation.

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In this episode, Kevin Hurley, CTO and co-founder of Lightspark, discusses the Layer 2 solution called Spark, which aims to enhance Bitcoin's scalability and user experience. He shares insights from his journey transitioning from the Libra project to building on Bitcoin, addressing challenges faced with the Lightning Network, and the unique features of Spark, including its architecture, user experience, and future developments. The conversation also touches on trust, privacy, tokenization, and the importance of community engagement in the Spark ecosystem.

Takeaways:

🔸Spark aims to provide a scalable and user-friendly Layer 2 solution for Bitcoin.

🔸The transition from Libra to Bitcoin was driven by the need for a decentralized settlement layer.

🔸Challenges with the Lightning Network include inbound liquidity and complexity for users.

🔸Spark simplifies the user experience by abstracting away complexities of the Lightning Network.

🔸Unilateral exits in Spark allow users to retrieve funds without operator involvement.

🔸The architecture of Spark is designed to support high transaction throughput and scalability.

🔸Privacy features are being developed to enhance user confidentiality in Spark transactions.

🔸Tokenization on Spark allows for the creation and transfer of assets efficiently.

🔸The Spark ecosystem encourages community involvement and developer contributions.

🔸Future developments will focus on programmability and advanced financial functionalities.

Timestamps:

(00:00) - Intro

(01:01) - Kevin’s journey from Libra to Bitcoin

(04:28) - Why the need for another L2?

(07:49) - What is @spark?; How is it beneficial for the end user?

(12:09) - Spark's technical framework

(20:40) - Cooperative exits vs. Unilateral exits

(26:17) - Sponsor

(27:10) - Trust & privacy considerations in Spark

(29:16) - Enhancing privacy in transactions

(34:48) - Developer experience & tooling

(36:37) - What is Spark’s token protocol (BTKN)?

(39:11) - Stablecoin support on BTKN?

(41:13) - Kevin’s views on programmability with Spark

(43:35) - How is Spark different from other Layer 2 solutions?

(46:06) - What are Universal Money Addresses?; UMA for Cross-border transactions

(49:14) - Corporate chains vs. Neutral settlement layers

(52:15) - Can an individual spin up their own Spark operator?

(53:24) - Could 100 million people be using Spark?

(55:00) - How can one contribute to Spark?

Links:

Sponsor:

CoinKite.com (code LIVERA)

Stephan Livera links: