Merge pull request 0xPolygon#532 from 0xPolygon/empieichO-docs-review

zkEVM: Adding "Proving system inputs" doc

Author: EmpieichO

docs/img/zkEVM/psi-prover-sends-to-verif-sc.png

@@ -0,0 +1,48 @@
+Generating a proof for the valid processing of a single batch requires multiple inputs.
+
+In addition to the data from each transaction in the processed batch, other inputs are necessary to ensure the network's overall security.
+
+For example, some inputs need to be sent to the smart contract.
+
+Central to generation of proofs and their verification are the verifier smart contract and the prover, as well as their interaction.
+
+This document, therefore, explores what the prover transmits to the verifier smart contract and why.
+
+In the zkEVM context, the focus is on generating _succinct_[^1] proofs rather than privacy concerns. 
+
+Consequently, L2 transactions and L2 state data are public. 
+
+We therefore delve into the initial design of the proving system, which operates without private inputs.
+
+## Public inputs
+
+Recall that the prover generates a proof, and sends the proof and an array of public inputs, denoted by $\texttt{[publics]}$ to the smart contract. The figure below depicts this.
+
+![Figure: _ ](../../../img/zkEVM/psi-prover-sends-to-verif-sc.png)
+
+The public inputs consist of the following data:
+
+- `batchData` which is the data of all the L2 transactions in the batch being proved.
+
+- `currentStateRoot` referring to the current L2 state root.
+
+- `proverAccount` which is the prover's account due to receive rewards. This account is attached to the proof so as to avoid successful plagiariasm of the proof.
+
+- `timestamp` specifies the time at which the proof was generated.
+
+- `forkId` is the current version of the L2 EVM being used.
+
+- `chainId` is the identifier of the chain for which the proof is being generated. The protocol is designed with the capability to host multiple layer 2 networks.
+
+The public output of this process is a new L2 state root, denoted by `newStateRoot`.
+
+The prover does not send all these public inputs to the L1 smart contract. Some inputs are already stored in the contract. These include: `currentStateRoot`, `forkId`, and `chainId`.
+
+The rest of the inputs need to be included in the `calldata` of the transaction sent to the L1’s smart contract. That is, `batchData`, `timestamp`, `newStateRoot`.
+
+Since the `proverAccount` is included in the L1 transaction’s signature, it need not be explicitly provided.
+
+Finally, the prover also sends the proof of correct execution of all L2 transactions within the batch.
+
+
+[^1]: The term [_succinct_](https://www.di.ens.fr/~nitulesc/files/Survey-SNARKs.pdf) refers to the size of the proof being very small compared to the size of the statement or the witness (i.e., the size of the computation itself).

docs/zkEVM/architecture/proving-inputs/index.md

@@ -212,6 +212,8 @@ nav:
           - Recapitulation: zkEVM/architecture/proving-system/prover-and-verifier-recap.md
         - L2 state tree concept: 
           - L2 state tree concept: zkEVM/architecture/l2-state-tree/index.md
+        - Proving system inputs:
+          - Proving system inputs: zkEVM/architecture/proving-inputs/index.md
         - zkProver:
           - zkProver: zkEVM/architecture/zkprover/index.md
           - Main state machine: