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Unofficial Scroll ZK EVM Code Review https://linktr.ee/alexcj96

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Summary - Why ZK EVM works? - Architecture - Tech stack comparaison - Arithmetization - Trace generation - Gate configuration - Circuit tools - Some opcode gadgets - Public input circuit - Synthesize - Combining with halo2 - Observation

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Why ZK EVM works? ❖ EVM is a State Machine ❖ Public-key cryptography ➢ Verify txs all represent users' intention ❖ Blockchain consensus ➢ Verifier ➢ Previous state root ❖ MPT ➢ Verify initial state ➢ Verify new root ❖ ZK ➢ Succinctness ➢ Lookup Arguments ❖ Ethereum as a DA Layer

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Architecture

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Tech stack comparaison

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Arithmetization

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Trace generation - flow (scroll has simplified this)

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Trace generation - types (simplified)

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Gate configuration - flow

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Gate configuration - gadgets Add cb constraints etc

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Gate configuration - lookup

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Circuit tools - cell manager

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Circuit tools - constraint builder

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Circuit tools - constraint builder

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Circuit tools - utils

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Some opcode gadgets - AddSub

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Some opcode gadgets - ReturnRevert (simplified)

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Public input circuit

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Public input circuit

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Synthesize

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Combining with halo2

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Combining with halo2

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Observation - Scroll doesn’t support self destruct EVM opcode - Scroll’s MPT tree uses poseidon circuit - Scroll uses chain_id and block_number to calculate block_hash!!! - Scroll still uses SuperCircuit which is very zk-unfriendly - Don’t read PSE’s code, it’s not production ready!!! - …

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Thanks!