Spark is a variant of Statechains. Statechains are an original second-layer protocol originally developed by Ruben Somsen in 2018. Statechains are a proposed off-chain system that allows a user (such as Alice) to delegate the ability to spend a UTXO to another user (Bob), who can then further delegate the spending authority to a third user (Carol), and so on. The off-chain delegation operations are all performed using signature adaptors and the cooperation of a trusted third party who employs the eltoo mechanism—and their knowledge of every previous delegation—to ensure each new delegation uses a state number higher than any previously used state number. These incrementing state numbers ensure that an on-chain spend by the most recent delegate (Carol) can take precedence over spends by previous delegates (Alice and Bob), provided the trusted third party hasn’t colluded with a previous delegate to cheat. Beyond collusion with a delegated signer (such as Alice or Bob), there is no way for the trusted third party to steal funds. A delegated signer can always spend the UTXO on-chain without needing permission from the trusted third party, arguably making Statechains less trusted than federated sidechains. We can think of Statechains as a digital version of Opendime. We know that Statechains can’t provide the same trustless self-custody as the Lightning Network, but we still like them. Statechains can be part of the Lightning Network. https://medium.com/@RubenSomsen/statechains-non-custodial-off-chain-bitcoin-transfer-1ae4845a4a39

Bitcoin Optech

Statechains

Statechains are a proposed offchain system for allowing a user (such as Alice) to delegate the ability to spend a UTXO to another user (Bob), who c...

OPENDIME™ – World's First Bitcoin Credit Stick Wallet

OPENDIME™ – World's First Bitcoin Credit Stick Wallet

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Bitcoin Magazine

Bitcoin Layer 2: Statechains

The second article in the Bitcoin Layer 2 series. This article covers Statechains, originally designed by Ruben Somsen, and implemented by Commerce...

Build Stablecoin Apps & Bitcoin Wallets with Spark SDKs - *Spark

Create Bitcoin-native wallets, launch stablecoins, and build fast, low-cost financial apps with Spark. No bridges. No wrappers. Purely on Bitcoin.