Second, a brand new Bitcoin improvement 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 “Quick, low-fee, self-custodial” pockets.
Alongside Grubles, different former Blockstream workers have joined the Second, reminiscent of 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 trade, 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 Second’s customized implementation of the Ark protocol, designed for interoperability with the Lightning Community.
“The method used for Bark is completely different from fee channels in Lightning, however the two are literally very complementary.” Grubles informed Bitcoin Journal in an unique interview, including that “At Second, we’ve chosen to construct an Ark that’s targeted solely on making Bitcoin onboarding and funds wonderful.” 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.
In accordance with Grubles, the corporate has raised 5.1M from a personal investor, with a workforce of 11 folks engaged on Bark. Deep technical documentation concerning the undertaking may be discovered at second.tech, with the principle internet 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 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 executed 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 solely.
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 instances a day. To cite Knifefight’s wonderful 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 relatively awkward, as wallets appropriately 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 at the moment — nonetheless requires a big studying curve, or specialised {hardware} that pushes all the proper 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 situations, whereas in addition 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 alternate options. The app is non KYCed, and gives 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 fee is as simple 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 just too excessive a price when making an attempt to promote Bitcoin as digital money, and making an attempt to onboard new folks on the spot.
Different corporations have tried to resolve these scaling and consumer expertise challenges by leveraging Blockstream’s Liquid Community, a global 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 verify a transaction after which supply them a built-in swap change to onchain BTC, or the Lightning Community for funds suitable 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 fee 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 as compared, contemplating the way you gained’t have to differentiate between L-BTC and BTC,” mentioned Grubles of present Liquid and Lightning options. “That is necessary when pondering of onboarding new Bitcoin customers. You don’t wish to bombard them with data that may be complicated.”
“Don’t get me fallacious, we love Lightning,” added Grubles, explaining that “Many people at Second have labored on initiatives like Blockstream’s Core Lightning or are at present 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’ll be able to 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 motive why I used to be interested in Second and the expertise 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 merely pre-signed transactions that assure the creation of an actual UTXO underneath 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, reminiscent of mass payouts,” mentioned 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 on the spot finality and low charges utilizing Bark. Mining swimming pools might additionally supply extra frequent payouts for his or her shoppers as an alternative of forcing them to attend a very long time as a result of onchain charges may be excessive.”
These vUTXOs perform in an identical approach as Lightning Community transactions, shifting offchain with an choice to settle to the principle 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 principle trade-off made by Ark-style protocols, and its dangers are mitigated by shifting all self-custody-related energy to the tip consumer in what is commonly described as “unilateral exit” capabilities.
Shinobi additional defined the trade-offs of Ark, saying, “The protocol is determined by a central coordinating server with the intention to perform correctly, however regardless of that, it is ready to present the identical performance and safety ensures that the Lightning Community does.” Much like Lightning, self-custody is ruled by a type 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. “So long as a consumer stays on-line through the required time interval,” Shinobi provides, “(except they select to belief the operator for brief intervals 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 measurement, respecting the decentralization of the community, so customers can run full nodes, audit the complete provide and integrity of the chain, but additionally 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 is just not 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 not 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 may be costly, however cooperative offboards are the traditional path,” including that “I believe the breakthrough goes to come back right down to execution. So long as we’re managing our Lightning gateway properly and have a dependable SDK, the elements are there to ship a bitcoin fee UX that beats every part else on the market. Our expectation is that Bark turns into the default approach finish customers have interaction with the Lightning Community.”
