SecondHQ, a brand new Bitcoin improvement lab, has gained consideration just lately because it drew in one more former Blockstream worker referred to as “Grubles”, with over 8 years of engineering on the firm. Bark, SecondHQ’s lead product, guarantees to ship a next-generation “Quick, low-fee, self-custodial” pockets.
Alongside Grubles, different former Blockstream workers have joined the SecondHQ, corresponding to Neil Woodfine (CMO), Steven Roose (CEO), and Erik De Smedt (CTO). The lab is at the moment 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 completely different trade-offs than the Lightning Community to ship finish customers scalable self-custody and funds options at a low value. Bark is SecondHQ’s customized implementation of the Ark protocol, designed for interoperability with the Lightning Community.
“The method used for Bark is completely different from cost channels in Lightning, however the two are literally very complementary.” Grubles advised Bitcoin Journal in an unique interview, including that “At Second, we’ve chosen to construct an Ark that’s targeted totally on making Bitcoin onboarding and funds glorious.” Their web site describes an Ark-to-Lightning bridge that lets customers pay Lightning invoices straight from an Ark stability with no channels, liquidity, or LSPs required. Dealt with atomically.
Based on Grubles, the corporate has raised 5.1M from a personal investor, with a staff of 11 folks engaged on Bark. Deep technical documentation concerning the venture could be discovered at second.tech, with the primary internet launch anticipated “Quickly”.
customers can take a look at out making Bark funds on Signet. “I extremely suggest doing so because it’s such a shift in the way in which we are able to do onboarding and funds,” stated Grubles, encouraging early adopters to check out the tech.
Scaling Bitcoin Self-Custody
Essentially the most spectacular declare made by Bark is the promise of self-custody at a low value. 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 large 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 of per second, which doesn’t scale to too many customers if they’re all doing maxinym self custody onchain transactions a number of occasions a day. To cite Knifefight’s excellent 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/particular person each ~55 years, assuming nobody is born or dies whereas ready.” Onboarding customers with onchain Bitcoin will also be fairly awkward, as wallets accurately sign that deposits made to new customers are pending affirmation till confirmed, which might 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 probably the most half, it has labored, however with important trade-offs. Self internet hosting a sovereign Lightning node, — whereas simpler than ever right now — nonetheless requires a big studying curve, or specialised {hardware} that pushes all the appropriate buttons for you. Each of those limitations 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 have to belief Phoenix with some excessive eventualities, whereas in addition they surrender a big quantity of privateness, since Acinq, the app developer, must know person balances pseudonymously to course of transactions. Customers are additionally locked into Phoenix as a liquidity supplier, paying typically larger charges than custodial lightning options. The app is non KYCed, and provides customers self-custody restoration paths, and an excellent feature set, however nonetheless falls wanting the person expertise anticipated from money, the place onboarding is as straightforward as handing a brand new person some paper cash — no liquidity challenges, channel managment or onboarding charges — and cost is as straightforward handing over a invoice and calculating the money again for change.
Phoenix particularly works very properly after customers have been onboarded, however the course of can value over $10 {dollars} in SATS and take over half-hour, which is simply too excessive a value when attempting to promote Bitcoin as digital money, and attempting to onboard new folks on the spot.
Different corporations have tried to unravel these scaling and person expertise challenges by leveraging Blockstream’s Liquid Community, a global federation of Bitcoin companies that function an alternate 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 might take a minute or much less to verify a transaction after which supply them a built-in swap trade 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 will 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 facet chain or Lightning channel administration.
“I believe the UI for Bark wallets will probably be simplified compared, contemplating the way you received’t have to differentiate between L-BTC and BTC,” stated Grubles of present Liquid and Lightning options. “That is essential when pondering of onboarding new Bitcoin customers. You don’t need to bombard them with info that may be complicated.”
“Don’t get me flawed, we love Lightning,” added Grubles, explaining that “Many people at Second have labored on initiatives like Blockstream’s Core Lightning or are at the moment engaged on issues just like the rust-lightning library…So I don’t say it calmly that Lightning is in Second’s DNA. With a Bark pockets, you possibly can obtain some bitcoin and start doing Lightning funds actually in seconds. The entire liquidity micromanagement is gone. The onboarding potential is big, and a big cause why I used to be interested in SecondHQ and the expertise in Bark.”
The Digital UTXO
As an implementation of the Ark protocol, SecondHQ’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 merely pre-signed transactions that assure the creation of an actual UTXO underneath the unilateral management of a person as soon as submitted onchain, however are in any other case held offchain.”
“There are different thrilling issues you are able to do with VTXOs, corresponding to mass payouts,” stated Grubles of the scalability of Bark. “Think about you’re an employer and have to course of payroll. That’s one thing you are able to do with prompt finality and low charges utilizing Bark. Mining swimming pools might additionally supply extra frequent payouts for his or her purchasers as an alternative of forcing them to attend a very long time as a result of onchain charges could be excessive.”
These vUTXOs perform in an identical method as Lightning Community transactions, shifting 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 shifting all self-custody-related energy to the tip person in what is commonly described as “unilateral exit” capabilities.
Shinobi additional defined the trade-offs of Ark, saying, “The protocol will depend on a central coordinating server with a purpose to perform correctly, however regardless of that, it is ready to present the identical performance and safety ensures that the Lightning Community does.” Just like Lightning, self-custody is ruled by a form of good contract with a number of folks concerned and a time constraint, on this case, the Ark operators, every person, and a spherical to refresh vUTXO’s each month or two. “So long as a person stays on-line in the course of the required time interval,” Shinobi provides, “(until they select to belief the operator for brief durations of time) each person is able to unilaterally exiting the Ark system at any time and taking again full unilateral management 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 just isn’t solely manageable however extra lenient than that of the Lightning Community; “There are actual tradeoffs like with any scaling resolution. Wallets want to come back on-line at the least as soon as a month (although Lightning technically requires always-on to be safe). Emergency exits require a number of onchain transactions and could be costly, however cooperative offboards are the conventional path,” including that “I believe the breakthrough goes to come back all the way down to execution. So long as we’re managing our Lightning gateway properly and have a dependable SDK, the components are there to ship a bitcoin cost UX that beats all the things else on the market. Our expectation is that Bark turns into the default method finish customers interact with the Lightning Community.”
