SecondHQ, a brand new Bitcoin growth lab, has gained consideration just lately because it drew in one more former Blockstream worker generally known 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, equivalent 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 know-how. 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 SecondHQ’s customized implementation of the Ark protocol, designed for interoperability with the Lightning Community.
“The approach used for Bark is totally different from cost channels in Lightning, however the two are literally very complementary.” Grubles instructed Bitcoin Journal in an unique interview, including that “At Second, we’ve chosen to construct an Ark that’s targeted fully 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 steadiness with no channels, liquidity, or LSPs required. Dealt with atomically.
In line with Grubles, the corporate has raised 5.1M from a personal investor, with a staff of 11 individuals engaged on Bark. Deep technical documentation in regards to the challenge might be discovered at second.tech, with the primary web launch anticipated “Quickly”.
customers can check 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,” 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 carried out now by the funds big Money App. Delivering self-custody for comparatively small quantities of worth to tens of millions of individuals is one other matter fully.
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 instances 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/particular person each ~55 years, assuming nobody is born or dies whereas ready.” Onboarding customers with onchain Bitcoin may also be quite 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 handle 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 in the present day — nonetheless requires a big studying curve, or specialised {hardware} that pushes all the suitable buttons for you. Each of those boundaries 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 quit 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 typically greater charges than custodial lightning options. The app is non KYCed, and provides customers self-custody restoration paths, and a very good characteristic 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 effectively 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 making an attempt to promote Bitcoin as digital money, and making an attempt to onboard new individuals 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 companies that function another Bitcoin-compatible blockchain with quick block instances 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 substantiate a transaction after which provide them a built-in swap alternate 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 facet chain or Lightning channel administration.
“I feel the UI for Bark wallets might be simplified as compared, contemplating the way you gained’t must differentiate between L-BTC and BTC,” mentioned Grubles of present Liquid and Lightning options. “That is necessary when considering of onboarding new Bitcoin customers. You don’t need to bombard them with info that may be complicated.”
“Don’t get me improper, we love Lightning,” added Grubles, explaining that “Many people at Second have labored on tasks like Blockstream’s Core Lightning or are at present engaged on issues just like the rust-lightning library…So I don’t say it evenly 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. All the liquidity micromanagement is gone. The onboarding potential is large, and a big purpose why I used to be drawn to SecondHQ and the know-how 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 in regards to the Ark protocol in 2025 intimately, explaining that vUTXOs “are merely pre-signed transactions that assure the creation of an actual UTXO below the unilateral management of a consumer 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, equivalent to mass payouts,” mentioned Grubles of the scalability of Bark. “Think about you’re an employer and must course of payroll. That’s one thing you are able to do with instantaneous finality and low charges utilizing Bark. Mining swimming pools may additionally provide extra frequent payouts for his or her shoppers as a substitute of forcing them to attend a very long time as a result of onchain charges might be excessive.”
These vUTXOs operate in an analogous 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 tip consumer in what is usually described as “unilateral exit” capabilities.
Shinobi additional defined the trade-offs of Ark, saying, “The protocol is dependent upon a central coordinating server with a purpose to operate 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 individuals concerned and a time constraint, on this case, the Ark operators, every consumer, and a spherical to refresh vUTXO’s each month or two. “So long as a consumer stays on-line throughout the required time interval,” Shinobi provides, “(except they select to belief the operator for brief durations of time) each consumer 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 total 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 actual tradeoffs like with any scaling answer. Wallets want to come back on-line no less than as soon as a month (although Lightning technically requires always-on to be safe). Emergency exits require a number of onchain transactions and might be costly, however cooperative offboards are the traditional path,” including that “I feel the breakthrough goes to come back all the way down to execution. So long as we’re managing our Lightning gateway effectively and have a dependable SDK, the elements are there to ship a bitcoin cost UX that beats every little thing else on the market. Our expectation is that Bark turns into the default manner finish customers interact with the Lightning Community.”