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Ark

Ark protocol

A second-layer Bitcoin protocol that uses a shared UTXO and a coordinator to let users transact off-chain without opening channels.

Ark is a proposed off-chain payment protocol for Bitcoin. Users deposit into a shared output controlled by a coordinator (called the Ark Service Provider), receive virtual UTXOs ("vTXOs"), and can send those vTXOs to each other during an interactive process known as "round". At any time, a user can unilaterally exit back to an on-chain UTXO without the coordinator's cooperation.

Compared to Lightning, Ark does not require users to open channels, manage inbound liquidity, or stay online. The trade-off is that vTXOs have an expiry: if the user does not refresh them before the round ends, they have to exit on chain or risk to lose control of the funds.

The protocol is still under active research and development. The site arkdev.info collects current specifications and implementations such as arkade-os/arkd.

References