Ethereum: Prove on L1 that an ERC20 transfer event happened on L2

February 8, 2025 1:35 am Published by Munna

Verification of ERC20 transfer events in L1: an example of solidity

In this article, we will explore how to verify an ERC20 transfer event in the Ethereum layer 2 (L2) network using an intelligent solidity contract. We will assume that Alice transferred 100 USDC to Bob in a Block B transaction.

The problem: L1-Ética transactions in L2

When transferring assets between different blockchains, such as from L1 to L2, the transaction is executed in L1 and then spreads to L2 through a series of Esterscan transactions. However, this process can be inefficient due to the latency of the network and gas costs.

The ERC20 standard, which governs the transfer of tokens between accounts, has been updated to include support for L1-Eth transfers. However, verifying these events remains a challenge due to the decentralized nature of the Blockchain networks.

Our solution: A solidity contract

We will create a simple intelligent contract in solidity that demonstrates how to verify an ERC20 transfer event in L1 using an L2 network (arbitrum one or optimism). The contract will track all transactions that involve Bob and identify those with specific conditions, such as the sender that Alice and the recipient have transferred 100 USDC.

`SOLIDITY



Pragma solidity ^0.8.0;

Import "

L1tol2verifier contract {

    // MAPO DE ACCOUNTS TO YOUR HISTORY OF TRANSACTIONS

    mapping (address => transactionhistory) public transactions;

    Struct Transaccionhistory {

        Uint256 Blocknumber;

        Deaddress address;

        Taddress address;

        Uint256 quantity;

    }

    Transaction event created (Indexed Management Server, Indexed recipient address, Uint256 quantity);

    Transfer of events (indexed direction, indexed direction to the amount of UINT256);

    FUNCTION CREATETRASACTIONHISTORY () PUB PURE RETURNS (TRANSACTIONHISTORRY) {

        RETURN TRANSACCIONHISTORY (BLOCK.MESTAMP, MSG.SENDER, 0, 10010 * 18);

    }

    Sendransaction Function (_recipient, Uint256 _amount) payable public {

        // Create a transaction history for the sender

        transactions [msg.sender] .blocknumber = block.number;

        transactions [msg.sender] .fromaddress = _recipient;

        // Update the recipient's transaction history

        Transactions [_recipient] .amount += _amount;

    }

    FUNCTION VERIFYTRANSACTIONEVENT (_SENDER, _RECIPIENT) Public Returns (BOOL) {

        // Obtain the sender and the recipient of the transfer history of the L1 account

        Transactionhistory sender = transactions [msg.sender];

        Transactionhistory recipient = transactions [_recipient];

        // Verify if the sender is Alice

        Require (sender.fromaddress == "0x ...", "not valid");

        // Verify if the recipient has transferred 100 USDC

        Require (recipient.amount> = 10010 * 18, "the recipient did not transfer enough tokens");

        // Create a new event for the transfer of transfer (it is not shown in this example)

        transfers emits (sender.fromaddress, _recipient, 10010 * 18);

        return true;

    }

}



Explanation

This solidity contract consists of three main functions:

Createtransactionhistory: Create a new transactions history for an account.

Sendransaction: Send a transaction from one address to another and update its transaction records.

Verifytransactionevent`: Verify whether a specific transfer event occurs in the L1 (Ethereum) network using the sender provided and the addresses of the recipient.

The contract uses the mapping to store all transactions that involve Bob, including its transaction history.

Deployment

To implement this contract, you must:

Establish an Ethereum tap account.

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This post was written by Munna

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