Second, a brand new Bitcoin growth lab, has gained consideration lately because it drew in yet one more former Blockstream worker often called “Grubles”, with over 8 years of engineering on the firm. Bark, Second’s lead product, guarantees to ship a next-generation “Fast, low-fee, self-custodial” pockets.
Alongside Grubles, different former Blockstream staff have joined the Second, akin to Neil Woodfine (CMO), Steven Roose (CEO), and Erik De Smedt (CTO). The lab is at present targeted on the cutting-edge of end-user Bitcoin pockets expertise. On this area of interest of the business, the Ark protocol is the brand new child on the block, a layer two funds protocol that makes totally different trade-offs than the Lightning Community to ship finish customers scalable self-custody and funds options at a low price. Bark is Second’s customized implementation of the Ark protocol, designed for interoperability with the Lightning Community.
“The technique used for Bark is different from payment channels in Lightning, but the two are actually very complementary.” Grubles informed Bitcoin Journal in an unique interview, including that “At Second, we’ve chosen to build an Ark that is focused entirely on making Bitcoin onboarding and payments excellent.” Their web site describes an Ark-to-Lightning bridge that lets customers pay Lightning invoices immediately from an Ark steadiness with no channels, liquidity, or LSPs required. Dealt with atomically.
Based on Grubles, the corporate has raised 5.1M from a non-public investor, with a crew of 11 folks engaged on Bark. Deep technical documentation concerning the undertaking could be discovered at second.tech, with the primary internet launch anticipated “Soon”.
customers can check out making Bark funds on Signet. “I highly recommend doing so since it’s such a shift in the way we can do onboarding and payments,” mentioned Grubles, encouraging early adopters to check out the tech.
Scaling Bitcoin Self-Custody
Probably the most spectacular declare made by Bark is the promise of self-custody at a low price. Whereas it’s comparatively trivial to scale Bitcoin funds in a custodial method, as demonstrated by apps like Pockets of Satoshi, or as is being accomplished now by the funds big Money App. Delivering self-custody for comparatively small quantities of worth to hundreds of thousands of individuals is one other matter totally.
Onchain Bitcoin can deal with roughly 7 transactions per second, which doesn’t scale to too many customers if they’re all doing most self-custody on-chain transactions a number of occasions a day. To cite Knifefight’s glorious article on the matter on Bitcoin Journal, tittled “Free As In Freedom Is Not Free As In Beer”; “Bitcoin confirms ~0.4M transactions/day. That’s one transaction/person every ~55 years, assuming no one is born or dies while waiting.” Onboarding customers with onchain Bitcoin will also be reasonably awkward, as wallets accurately sign that deposits made to new customers are pending affirmation till confirmed, which may take as much as half-hour whereas blocks are mined.
To deal with the challenges of scaling Bitcoin funds to the entire world, whereas retaining the cypherpunk and decentralization qualities of onchain self-custody, the Lightning Community was developed, and for essentially the most half, it has labored, however with vital trade-offs. Self internet hosting a sovereign Lightning node, — whereas simpler than ever immediately — nonetheless requires a big studying curve, or specialised {hardware} that pushes all the fitting buttons for you. Each of those obstacles to entry are an excessive amount of for most individuals who don’t care about tech and simply want to have the ability to pay a invoice securely.
Cellular wallets like Phoenix have taken Lightning Community-style self-custody to finish customers, however with some caveats. Customers must belief Phoenix with some excessive situations, whereas additionally they surrender a big quantity of privateness, since Acinq, the app developer, must know consumer balances pseudonymously to course of transactions. Customers are additionally locked into Phoenix as a liquidity supplier, paying usually greater charges than custodial lightning options. The app is non KYCed, and provides customers self-custody restoration paths, and a very good function set, however nonetheless falls in need of the consumer expertise anticipated from money, the place onboarding is as simple as handing a brand new consumer some paper cash — no liquidity challenges, channel managment or onboarding charges — and cost is as simple handing over a invoice and calculating the money again for change.
Phoenix particularly works very nicely after customers have been onboarded, however the course of can price over $10 {dollars} in SATS and take over half-hour, which is just too excessive a value when attempting to promote Bitcoin as digital money, and attempting to onboard new folks on the spot.
Different firms have tried to resolve these scaling and consumer expertise challenges by leveraging Blockstream’s Liquid Community, a world federation of Bitcoin firms that function another Bitcoin-compatible blockchain with quick block occasions and far bigger on-chain capability. Wallets like Bull Bitcoin or Aqua onboard customers with Liquid’s LBTC, which may take a minute or much less to substantiate a transaction after which provide them a built-in swap change to onchain BTC, or the Lightning Community for funds appropriate with the broader Bitcoin market.
Each of those options work okay, however Bark believes they’ll do higher. The cheap self-custody restoration paths that onchain Bitcoin customers know and love, with the moment cost velocity of the Lightning Community, are each delivered upon app obtain to customers, with out the onboarding roadblocks of a Liquid aspect chain or Lightning channel administration.
“I think the UI for Bark wallets will be simplified in comparison, considering how you won’t need to differentiate between L-BTC and BTC,” mentioned Grubles of present Liquid and Lightning options. “This is important when thinking of onboarding new Bitcoin users. You don’t want to bombard them with information that can be confusing.”
“Don’t get me wrong, we love Lightning,” added Grubles, explaining that “Many of us at Second have worked on projects like Blockstream’s Core Lightning or are currently working on things like the rust-lightning library…So I do not say it lightly that Lightning is in Second’s DNA. With a Bark wallet, you can receive some bitcoin and begin doing Lightning payments literally in seconds. All of the liquidity micromanagement is gone. The onboarding potential is huge, and a large reason why I was attracted to Second and the technology in Bark.”
The Digital UTXO
As an implementation of the Ark protocol, Second’s Bark lets customers pay one another with Digital Unspent Transaction Outputs, or vUTXOs. Shinobi, the Technical Author for Bitcoin Journal, wrote concerning the Ark protocol in 2025 intimately, explaining that vUTXOs “are simply pre-signed transactions that guarantee the creation of a real UTXO under the unilateral control of a user once submitted onchain, but are otherwise held offchain.”
“There are other exciting things you can do with VTXOs, such as mass payouts,” mentioned Grubles of the scalability of Bark. “Imagine you’re an employer and need to process payroll. That’s something you can do with instant finality and low fees using Bark. Mining pools could also offer more frequent payouts for their clients instead of forcing them to wait a long time because onchain fees can be high.”
These vUTXOs operate in an identical manner as Lightning Community transactions, transferring offchain with an choice to settle to the primary Bitcoin blockchain when wanted. Although not like the Lightning Community, every Ark implementation has a centralized coordination server that enhances the service, that is the primary trade-off made by Ark-style protocols, and its dangers are mitigated by transferring all self-custody-related energy to the top consumer in what is usually described as “unilateral exit” capabilities.
Shinobi additional defined the trade-offs of Ark, saying, “The protocol depends on a central coordinating server in order to function properly, but despite that, it is able to provide the same functionality and security guarantees that the Lightning Network does.” Just like Lightning, self-custody is ruled by a form of sensible contract with a number of folks concerned and a time constraint, on this case, the Ark operators, every consumer, and a spherical to refresh vUTXO’s each month or two. “As long as a user stays online during the required time period,” Shinobi provides, “(unless they choose to trust the operator for short periods of time) every user is capable of unilaterally exiting the Ark system at any time and taking back full unilateral control of their funds on-chain.”
This unilateral exit is the very definition of self-custody within the context of Bitcoin. By enabling it offchain, it bypasses the constraints of Bitcoin’s block dimension, respecting the decentralization of the community, so customers can run full nodes, audit the complete provide and integrity of the chain, but in addition entry unprecedented ranges of sovereignty over their cash, even in a future the place the charges are excessive and the blocks are full.
Grubles believes the time constraint in Bark shouldn’t be solely manageable however extra lenient than that of the Lightning Community; “There are real tradeoffs like with any scaling solution. Wallets need to come online at least once a month (though Lightning technically requires always-on to be secure). Emergency exits require multiple onchain transactions and can be expensive, but cooperative offboards are the normal path,” including that “I think the breakthrough is going to come down to execution. As long as we’re managing our Lightning gateway well and have a reliable SDK, the ingredients are there to deliver a bitcoin payment UX that beats everything else out there. Our expectation is that Bark becomes the default way end users engage with the Lightning Network.”
