> For the complete documentation index, see [llms.txt](https://docs-zkevm.cronos.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs-zkevm.cronos.com/for-developers/using-zkcro-veth-and-vusd/zkcro.md).

# zkCRO

{% hint style="danger" %}
**Notice: Cronos zkEVM is being sunset, please** [**bridge out your assets**](/for-developers/using-zkcro-veth-and-vusd/zkcro.md#l2-greater-than-l1-withdrawing-usdzkcro-from-l2) **before the network is fully decommissioned.**
{% endhint %}

[#l2-greater-than-l1-withdrawing-usdzkcro-from-l2](#l2-greater-than-l1-withdrawing-usdzkcro-from-l2 "mention")

[#l2-greater-than-l1-withdraw-eth-from-veth](#l2-greater-than-l1-withdraw-eth-from-veth "mention")

***

## \[L2 -> L1] Withdrawing $zkCRO from L2

*From Cronos zkEVM mainnet (L2) -> Ethereum mainnet (L1)*

To withdraw $zkCRO from`Cronos zkEVM mainnet -> Ethereum mainnet`, we would need to interact with the following contract:

* $zkCRO token contract:
  * Cronos zkEVM: [`0x000000000000000000000000000000000000800a`](https://explorer.zkevm.cronos.org/address/0x000000000000000000000000000000000000800a)
* zkChain Shared Bridge:
  * Ethereum : [0xD7f9f54194C633F36CCD5F3da84ad4a1c38cB2cB](https://etherscan.io/address/0xD7f9f54194C633F36CCD5F3da84ad4a1c38cB2cB)

### Step 1) Initiating a withdrawal transaction

On Cronos zkEvm, call the `withdraw` function of zkCRO token contract:

```
function withdraw(address _l1Receiver) external payable;
```

| Parameters    | Comments                                         |
| ------------- | ------------------------------------------------ |
| `_l1Receiver` | The address to recieve zkCRO on Ethereum mainnet |
| `payable`     | The amount of $zkCRO to be transfer.             |

It will take at least 24 hours before the withdrawal can be finalized on Ethereum. Store the transaction hash from the withdrawal transaction for later steps.

### Step 2) Gathering information for $zkCRO withdrawal on L1

Extra information for the L2 -> L1 transaction is required for the next step in claiming the $zkCRO on L1. This information can be gathered by [finalizeWithdrawalParams](https://docs.zksync.io/sdk/js/ethers/api/v5/accounts/wallet#finalizewithdrawalparams), using `zksync-ethers` package

```
finalizeWithdrawalParams(withdrawalHash)
```

This takes the L2 withdrawal hash as parameters and returns the parameters required for finalizing a withdrawal in the next step.

Example outputs:

```
{
  l1BatchNumber: 18,
  l2MessageIndex: 59,
  l2TxNumberInBlock: 2919,
  message: '0x6c0960f935f448644c86dbda241ecb57f18a15c80f35a066000000000000000000000000000000000000000000000a2a15d09519be000000',
  sender: '0x000000000000000000000000000000000000800a',
  proof: [
    '0x23ff0fb003a6a6e111f87cff02afc8680944c711abbe792f07ab4206e9efb9a3',
    '0x09fece9c46307f2a0976a3a9b57873e453cf0f4773c2377dcd19f054166aef22',
    '0x33c106ae5601983b53c751129d1921c17e40b69aa3fdbfaf07b7a0e0750d35e4',
    '0x952ffa5de22d99815d9513dd7454949edb2a1cbcf86008f6fa8b169ffe9b4aee',
    '0x8f10560a0b5412ca2e0578fb9266f55411f357d52c8fc3b2cad43b9877a559a6',
    '0x8e70b93d3c90798df26473a3ad32a86170e8d52023a4044cf1d4c2d645471b14',
    '0xdfaacb39891bbbf4509af408239b97a6f5ef715a5c299ba1f3625c20aec4ef8f',
    '0xb04e5ee349086985f74b73971ce9dfe76bbed95c84906c5dffd96504e1e5396c',
    '0xac506ecb5465659b3a927143f6d724f91d8d9c4bdb2463aee111d9aa869874db',
    '0x124b05ec272cecd7538fdafe53b6628d31188ffb6f345139aac3c3c1fd2e470f',
    '0xc3be9cbd19304d84cca3d045e06b8db3acd68c304fc9cd4cbffe6d18036cb13f',
    '0xfef7bd9f889811e59e4076a0174087135f080177302763019adaf531257e3a87',
    '0xa707d1c62d8be699d34cb74804fdd7b4c568b6c1a821066f126c680d4b83e00b',
    '0xf6e093070e0389d2e529d60fadb855fdded54976ec50ac709e3a36ceaa64c291'
  ]
}
```

### Step 3) Claiming the $zkCRO on L1

Once the transaction in Step 1 has been finalized on L1, we can claim the withdrawn $zkCRO from the zk Chain Shared Bridge contract by calling its `finalizeWithdrawal` function. The inputs can be found in Step 2,

```
    function finalizeWithdrawal(
            uint256   _chainId,
            uint256   _l2BatchNumber,
            uint256   _l2MessageIndex,
            uint16    _l2TxNumberInBatch,
            bytes calldata _message,
            bytes32 calldata _merkleProof
        )
```

| Parameters           | Comments                                                                                                 |
| -------------------- | -------------------------------------------------------------------------------------------------------- |
| `_chainId`           | Chain id for Cronos zkEVM, which is `388`                                                                |
| `_l2BatchNumber`     | The L2 batch number where the withdrawal was processed, obtained in Step 2.                              |
| `_l2MessageIndex`    | The position in the L2 logs Merkle tree of the l2Log that was sent with the message, obtained in Step 2. |
| `_l2TxNumberInBatch` | The L2 transaction number in the batch, in which the log was sent, obtained in Step 2.                   |
| `_message`           | The L2 withdraw data, stored in an L2 -> L1 message, obtained in Step 2.                                 |
| `_merkleProof`       | The Merkle Proof, obtained in Step 2.                                                                    |

Once `finalizeWithdrawal` is completed, the withdrawn amount of $zkCRO will go into the receiver's wallet on Ethereum.

We can use `zksync-ethers` package  [`isWithdrawalFinalized`](https://docs.zksync.io/sdk/js/ethers/api/v5/accounts/wallet#iswithdrawalfinalized) call to confirm whether the withdrawal transaction is finalized on the L1 network.

```
isWithdrawalFinalized(withdrawalHash)
```

| Parameters       | Comments                                                                                    |
| ---------------- | ------------------------------------------------------------------------------------------- |
| `withdrawalHash` | The transaction hash of the L2 transaction includes the withdrawal transaction from Step 1. |

{% hint style="info" %}
Note - If you would like to convert $zkCRO on Ethereum to $CRO, you can do so by unstaking it to obtain the underlying $CRO staked and receive the $CRO on "Cronos EVM Mainnet" . Please refer to the following guide [#l2-greater-than-l1-withdraw-eth-from-veth](#l2-greater-than-l1-withdraw-eth-from-veth "mention") to complete the process.
{% endhint %}

***

## Unstaking $zkCRO for $CRO <a href="#l2-greater-than-l1-withdraw-eth-from-veth" id="l2-greater-than-l1-withdraw-eth-from-veth"></a>

To redeem $zkCRO from`Ethereum mainnet` and receive the underlying unstaked $CRO ( on "[Cronos EVM Mainnet](https://docs.cronos.org/)"), we would need to interact with the following contracts:

* $zkCRO token contract
  * Ethereum: [0x28ff2e4dd1b58efeb0fc138602a28d5ae81e44e2](https://etherscan.io/address/0x28ff2e4dd1b58efeb0fc138602a28d5ae81e44e2)
* &#x20;$LCRO token contract
  * Cronos EVM Mainnet: [0x9fae23a2700feecd5b93e43fdbc03c76aa7c08a6](https://cronoscan.com/address/0x9fae23a2700feecd5b93e43fdbc03c76aa7c08a6)
* `vnoNFT`
  * Cronos EVM Mainnet: [0xb15533a0bc7c530d692a9660785226dfd3633965](https://cronoscan.com/address/0xb15533a0bc7c530d692a9660785226dfd3633965)

### Step 1) Approving $zkCRO to be spend by zkCRO token contract

On Ethereum, approve $zkCRO to be spent by zkCRO contract with appropriate amount.

### Step 2) Unstaking $zkCRO to recieve $LCRO

On Ethereum, call the `unstake` function on the zkCRO token contract:&#x20;

```
function unstake(
        address _receiver, 
        uint256 _shareAmount
        )
```

| Parameters     | Comments                                         |
| -------------- | ------------------------------------------------ |
| `_receiver`    | The Cronos EVM mainnet address to receive $LCRO. |
| `_shareAmount` | The amount of $zkCRO to unstake.                 |

Once done, $LCRO token will be automatically released within 24 hours and transfer to the `_receiver` address of "**Cronos EVM mainnet".**&#x20;

### Step 3) Approving $LCRO spent

On Cronos EVM mainnet, approve $LCRO to be spent by $LCRO contract with appropriate amount

### Step 4) Unbonding $LCRO

On Cronos EVM mainnet, call `requestUnbond` on the LCRO token contract,

```
function requestUnbond(
        uint256 _shareAmount, 
        address _receiver
        )
```

| Parameters     | Comments                                                                                                                        |
| -------------- | ------------------------------------------------------------------------------------------------------------------------------- |
| `_shareAmount` | The amount of $LCRO that is to be burned to unbond                                                                              |
| `_receiver`    | The wallet address on ethereum to receive the receipt NFT. This NFT is needed to withdraw $CRO once the unbond period has ended |

Once done you will receive an NFT (`vnoNFT`) in return. Wait for batch of unbonding to be processed which takes 28-32 days.

### Step 5) Approving NFT to be spend by LCRO contract

On Cronos EVM mainnet, call `setApprovalForAll` on the [vnoNFT contract](https://cronoscan.com/address/0xb15533a0bc7c530d692a9660785226dfd3633965#writeProxyContract), to approve to transfer  of the vnoNFT obtained in Step 4)

```
setApprovalForAll(
        address operator, 
        bool _approved
        )
```

| Parameters  | Comments                           |
| ----------- | ---------------------------------- |
| `operator`  | $LCRO contract address on ethereum |
| `_approved` | Set to "True" to grant approval.   |

### Step 6) Withdrawing $CRO

On Cronos EVM mainnet, call `unbond` function on the  LCRO token contract to burn the receipt NFT and receive the underlying unstaked $CRO.

```
 function unbond(
        uint256 _tokenId, 
        address _receiver
        )
```

| Parameters  | Comments                                           |
| ----------- | -------------------------------------------------- |
| `_tokenId`  | The tokenId of the receipt NFT, recieved in Step 4 |
| `_receiver` | The address on Cronos EVM mainnet to receive $CRO  |

This transaction burns the receipt NFT and sends the unstaked $CRO to the specified receiver.