Spark
Also · Spark operators · FROST
Spark is a Bitcoin layer 2 built on statechains. Users move bitcoin off-chain by sharing signing with a group of operators, keep an exit to Bitcoin, and reach Lightning through service providers.
Spark, announced by Lightspark in late 2024 and live since 2025, generalises the statechain. A user deposits bitcoin into an output whose key is split between them and a set of Spark operators using threshold signatures. Transferring the coin to someone else means re-sharing the key with the new owner and having the operators forget the old share, with no on-chain transaction. Payments are instant and nearly free.
The trust assumption is that at least 1 operator honestly deletes old key shares, since all of them colluding with a past owner could double spend. Each user holds a pre-signed exit transaction to Bitcoin. Service providers connect Spark to Lightning, so wallets built on it look and pay like Lightning wallets without channels or liquidity to manage. It is the layer behind a new wave of self-custodial wallets.
In French · Spark
