Imported from willyd61/nautobot-v2-custom-metrics-old (
.mcp-servers/skill-loader/skills/bitcoin/l2/ark/SKILL.md). Install upstream withnpx skills add willyd61/nautobot-v2-custom-metrics-old --skill ark. Copyright stays with the author.
Ark Protocol
Original concept: Burak (2023, posted to bitcoin-dev as TBDXXX).
Mainnet implementation: ARKADE (Ark Labs, public beta launched
2025-2026). Reference impl bark (Second).
Ark virtualizes Bitcoin's UTXO layer into VTXOs (Virtual Transaction Outputs) that are batched and settled periodically on chain.
Mechanism
Round-based architecture
- An ASP (Ark Service Provider) runs periodic rounds (e.g., every few minutes / hours).
- During each round, users send/receive funds via VTXOs.
- At round end, ASP commits the round state on chain via a single pool tx.
- Each user's VTXO is included in the pool tx as part of a Merkle/ binary tree structure.
VTXOs
A VTXO is a "virtual" output:
- Represented as a leaf in the round's tree.
- Spendable off-chain by sending it to another VTXO via ASP-mediated protocol.
- Has a CSV expiry: after the expiry, owner can unilaterally claim on chain via the round's commitment tx.
Unilateral exit
Even if ASP disappears:
- User can broadcast a chain of pre-signed txs to extract their VTXO from the round tree.
- Cost: linear in tree depth (typically log N).
- Time: limited by CSV expiry (typically days to weeks).
ARKADE features
Ark Labs' mainnet implementation:
- VTXO batches via taproot trees.
- Round time: ~5 seconds.
- ASP-coordinated cosigning protocol.
- Native BTC support; Arkade Assets for tokenized assets.
- V-PACK: stateless VTXO verification standard.
Bark (Second's impl)
Open source (MIT), in beta on signet/testnet:
- Wallet client for Ark.
- ASP server reference.
- Compatibility with ARKADE protocol.
Compared to Lightning
| Aspect | Lightning | Ark |
|---|---|---|
| Liquidity setup | Channel funding | None per user |
| Receiver inbound | Need pre-existing channel | None needed |
| Aggregator | n/a (peer-to-peer) | ASP (1 per round) |
| Settlement | Off-chain instant | Round-based (seconds to hours) |
| Exit cost | Channel close (~1 tx + per-HTLC) | Tree extraction (~log N txs) |
| Protocol type | Per-channel | Batched |
| Asset support | Optional (TAP, RGB layered) | Native (Arkade Assets) |
Use cases
- Receive without channel — user gets their first sats without pre-funded inbound.
- High-frequency micro-payments within rounds (no per-payment fee).
- Mobile-first — round-based, no need for always-online wallet.
- Asset issuance via Arkade Assets.
Status (late 2025)
- ARKADE mainnet in public beta.
- bark on signet.
- Ecosystem of wallets, services emerging.
- Active competing model with Spark, Lightning.
Limitations / trade-offs
- Round delay: payments confirmed within round time, not instant.
- ASP availability: ASP outage = unilateral-exit window.
- Tree depth scaling: log N exit cost; balanced trees keep this acceptable.
- Privacy: ASP sees all VTXO transfers in plaintext (compared to LN's onion routing).
