How Is Arbitrum Secured?
Arbitrum derives its security from the Ethereum network, which provides consensus and finality for Arbitrum transactions. In other words, Ethereum guarantees the validity of the rollup’s off-chain computation and data availability behind the computation.
The use of optimistic rollups means Arbitrum executes transactions on the rollup outside of Ethereum, and bundle multiple transactions in a batch before submitting it to mainnet. As the term “optimistic” suggests, the off-chain transactions are assumed to be valid and no proof-of-validity is submitted. In case of a dispute, there is a time period after the rollup is submitted where anyone can challenge the transaction by submitting a fraud proof.