Validiums are scaling solutions for Ethereum that use off-chain data availability and computation to process transactions more efficiently. Unlike zero-knowledge rollups (zk-rollups), which store some data on-chain, validiums keep transactions off-chain while using zero-knowledge proofs (ZKP) to verify their validity.
How Do Validiums Work?
Validiums operate by executing transactions off the Ethereum mainnet, leveraging smart contracts on Ethereum to ensure their validity and integrity. Letâs walk through some of the key aspects of validiums.
Transactions
When a user wants to make a transaction using a validium, they send it to an operator. Operators are nodes responsible for executing transactions on the validium chain. They could be a single entity or a group of entities chosen through a proof-of-stake (PoS) system.
The operator collects transactions into a batch and processes them off-chain. Once the batch is ready, the operator uses a special system called a proving circuit to create a proof that the transactions were performed correctly.
State commitments
Imagine Validiumâs state (the record of all accounts and their balances) as a big tree, known as a Merkle tree. The root of this tree, called the state root, is like a fingerprint that represents the entire state. This state root is stored on Ethereum.
When the operator processes transactions, they update the state root to reflect the new balances and account states. Then, they send this new state root along with the proof that everything was done correctly to the Ethereum mainnet.
Unlike zk-rollups, block producers on a validium donât need to publish all the transaction details on Ethereum. If Ethereum verifies the proof, the new state is accepted, and the validium is updated.
Deposits and withdrawals
Users can deposit their funds from Ethereum to a validium by sending ETH or other tokens to a special contract on Ethereum. The contract communicates this deposit to the validium off-chain and credits.
