Merge pull request 0xPolygon#517 from 0xPolygon/sc/verification-flow

zkEVM: High level architecture - smart contract verification flow

Author: EmpieichO

docs/img/cdk/high-level-architecture/verification-flow.png

@@ -1,2 +1,33 @@
-!!! warning
-    Coming soon.
+---
+comments: true
+---
+
+Transactions flowing through the system reach the smart contract environment after one of two contract call use-cases:
+
+- Sequence batches requests coming from the sequencer component in the node.
+- Verifying batches requests coming from the aggregator component in the node.
+
+This section focuses on the verification workflow. 
+
+The sequence diagram below shows the verification workflow for rollup stacks and/or the AggLayer calling the `verifyBatchesTrustedAggregator(...)` function on the rollup manager.
+
+![Polygon Solidity consensus verification flow](../../../../img/cdk/high-level-architecture/verification-flow.png)
+
+## `verifyBatchesTrustedAggregator(rollupID, pendingStateNum, initNumBatch, finalNewBatch, newLocalExitRoot, newStateRoot, beneficiary, proof)`
+
+This function is called on the `PolygonRollupManager` contract.
+
+The zkEVM node aggregator, or the AggLayer, calls the [`verifyBatchesTrustedAggregator`](https://github.com/0xPolygonHermez/zkevm-contracts/blob/b2a62e6af5738366e7494e8312184b1d6fdf287c/contracts/v2/PolygonRollupManager.sol#L921) function on the [`PolygonRollupManager.sol`](https://github.com/0xPolygonHermez/zkevm-contracts/blob/feature/etrog/contracts/v2/PolygonRollupManager.sol) contract.
+
+The function creates a rollup data storage object with the data provided by the caller, which it first verifies by sending it to the helper function [`_verifyAndRewardBatches`](https://github.com/0xPolygonHermez/zkevm-contracts/blob/b2a62e6af5738366e7494e8312184b1d6fdf287c/contracts/v2/PolygonRollupManager.sol#L977). 
+
+This internal function calculates the inputSnark bytes value, which is a `(SHA256 % "RFIELD")` calculation on the input data, and uses this value to verify the proof by calling `rollup.verifier.verifyProof(proof, [inputSnark])` on an `IVerifierRollup` interface implementation. 
+
+!!! note
+    Using a `verifier` variable on the rollup object means the verifier implementation can be customized in the future.
+
+Next, in the `_verifyAndRewardBatches` helper function, the code reverts if the proof does not verify successfully. Otherwise, the code pays POL rewards to the beneficiary. 
+
+The function then updates the state and calls `rollup.rollupContract.onVerifyBatches(...)`, which is a callback into the rollup consensus contract, allowing for customizable behavior. `onVerifyBatches(...)` takes the new state root and final batch, and emits a `VerifyBatches(...)` event.
+
+The command flow returns to the `verifyBatchesTrustedAggregator` function which consolidates and updates the state with the `newStateRoot` and the new `localExitRoot` and calls the `updateExitRoot(...)` function on the `GlobalExitRootManager` contract passing the rollup's updated exit root.

docs/zkEVM/architecture/high-level/smart-contracts/verification.md

@@ -95,7 +95,7 @@ nav:
           - Consensus contracts - sequencing: zkEVM/architecture/high-level/smart-contracts/sequencing.md
           - Bridging: zkEVM/architecture/high-level/smart-contracts/bridging.md
           - Exit roots: zkEVM/architecture/high-level/smart-contracts/exit-roots.md   
-          #- Consensus contracts - verification: zkEVM/architecture/high-level/smart-contracts/verification.md
+          - Consensus contracts - verification: zkEVM/architecture/high-level/smart-contracts/verification.md
           - API:
             - PolygonRollupManager.sol:  zkEVM/architecture/high-level/smart-contracts/api/PolygonRollupManager.md
             - PolygonZkEVMBridgeV2.sol:  zkEVM/architecture/high-level/smart-contracts/api/PolygonZkEVMBridgeV2.md