# Roll-Ups ## A Layer 1.5 Scaling Solution --- # Main Principle On-chain *transactions* Off-chain *state and computation* --- # Outline 1) Plasma 2) Roll-Ups 3) ZK and Optimistic 4) Throughput 5) Issues --- # Plasma - "Sidechain": - Operator collects transactions and computes state - Periodically commits state roots to main chain contract - Users enter and exit using on-chain transactions - Safety guarantee: Exit is always possible --- # Operator Attacks - Create invalid state: Fraud proofs - Create unavailable state: ? --- # Additional Issues - Censorship - Exit game limits expressability --- # Roll-Ups Same as Plasma, but different: - Transactions are stored on-chain - Safety guaranteed via fraud (optimistic) or validity (ZK) proofs - Single operator replaced by group of relayers - No exit game necessary --- # ZK Roll-Ups Pessimistic view - Validity of state needs to be proven - Proof usually zkSNARK --- # Optimistic RU Optimistic view - Any state is accepted - If proven to be invalid: - State is rolled back - Offending relayer is slashed --- # ZK vs Optimistic ZK Cons: - Reliance on zkSNARKS - Limited expressability OR Cons: - Slightly lower throughput - No immediate exit --- | Base Layer | Max Throughput [tx/s] | | -------- | -------- | | Eth 1 (pre Istanbul) | 0.25 k | | Eth 1 (post Istanbul) | 1 k | | Eth 2 Phase 1 | 100 k | (theoretical limits) --- # Disadvantages Not too many! - Throughput limited by layer 1 - Throughput limited by implementations - Risk of centralization - Ecosystem fragmentation --- # ?!