# Asset Bridge

Previously, we mentioned that users initially need to transfer assets to SatoshiVM to pay for transaction fees when initiating transaction requests within the Layer2 network. The bridging module of SatoshiVM is quite straightforward, currently mainly divided into deposit and withdrawal components.

### Assets Moving from Bitcoin to SatoshiVM Mainnet

In SatoshiVM terminology, transferring funds from Bitcoin (L1) to the SatoshiVM mainnet (L2) is called a deposit. Users need to transfer bitcoins to a deposit address specified by SatoshiVM. Once a deposit transaction is triggered on Layer1, the Layer2 Sequencer detects these deposit actions and subsequently incorporates them into Layer2 blocks, releasing an equivalent amount of assets to the user within the Layer2 network. Typically, such deposit transactions are processed within minutes after the Layer1 block is finally confirmed, generally waiting for the time equivalent to 6 Bitcoin blocks.

### Assets Moving from SatoshiVM Mainnet to Bitcoin

Compared to deposit transactions, withdrawing assets from L2 to L1 is more complex. Similarly to deposit transactions, any asset transfer from L2 to L1 is referred to as a withdrawal transaction.

Withdrawal transactions involve the following three steps:

1. The user initiates a Layer2 transaction, declaring a withdrawal and specifying the amount to be withdrawn.
2. After the Layer2 block containing this withdrawal transaction is finally confirmed, the user submits a withdrawal proof on Layer1, requesting the withdrawal of an equivalent amount of assets from a publicly managed account.
3. Waiting for the withdrawal challenge period to end (which can take several hours).


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