Also known as a "zero knowledge (ZK) proof," a validity proof is used by zero knowledge rollups (zk-Rollups) on Layer 2 blockchains to prove that the data summarized on the Layer 1 chain are valid. See
zero-knowledge proof and
Layer 2 blockchain.
Fraud Proofs
In contrast to validity proofs, fraud proofs are less complicated. Fraud proofs assume that the summarized Layer 2 transactions transferred to the Layer 1 chain are mostly valid. However, within a period of time, typically seven days, a fraud proof can be submitted that proves a false transaction. Fraud proofs are used in optimistic rollups, which along with zk-Rollups, are two major types of Layer 2 rollups. See
Optimism.