Bridge: Bitcoin
The Bitcoin Bridge allows users to transfer their Bitcoin from the Bitcoin network over to the Avalanche network. Bitcoin holders can directly access extensive earning and yield opportunities on top DeFi protocols on Avalanche, while still maintaining BTC on their portfolio.

How to Bridge your Bitcoin to Avalanche

Users can download the Core Wallet Extension to access BTC bridging. Unlike Metamask and other wallets, Core is custom built to support Bitcoin and the Avalanche Bridge.
Download Core Wallet App for Chrome here:
Core
Make sure you have Bitcoin to Bridge
If you don't have any Bitcoin head over to a centralized exchange like coinbase or binance and buy some! Once you have some Bitcoin, open the Core Wallet extension and click the "+" sign on the bottom and click "Bridge". Click "From: Bitcoin" on the drop down menu and click "Add Bitcoin"
Time to Bridge your Bitcoin
Copy your Core Bitcoin address from the menu and paste it into your Coinbase, Binance or other Wallet. The example below shows the process for Coinbase:
Finalising the Transaction
Once the transaction is confirmed, you will receive your native Bitcoin on Avalanche in you Core wallet. Click Bridge, Amount, Transfer. Congrats! You have now bridged and you will see your Bitcoin balance updated in your Wallet.
Transactions may take a number of minutes, depending on network activity

How the Bitcoin Bridge Works

To initiate bridging from Bitcoin to Avalanche, a transaction is sent on Bitcoin from the new Core Wallet that transfers BTC to the bridge address controlled only by the SGX enclave. The bridge is designed to only support Pay-To-Witness-Public-Key-Hash output types on Bitcoin. In order to ensure that the BTC transfer has this output type and meets all of the bridging requirements, users should always use the bridge UI in the Core Wallet extension that is built to provide a quick and easy bridging experience. Once this transaction is accepted into a block on Bitcoin and receives the necessary number of confirmations, it will be indexed by the Warden nodes and reported to the Intel SGX application for processing. The SGX enclave only processes transfers when it receives approvals from at least 6 of the 8 Warden nodes. At this point, the SGX application mints (creates) the equivalent amount of BTC.b to the user wallet that sent the initiating Bitcoin transaction.
Similarly, when moving BTC.b from Avalanche back to Bitcoin, the user sends a transaction on Avalanche that calls the “unwrap” method of the BTC.b contract, which burns (destroys) the BTC.b tokens. The Warden nodes will index this transaction, and it will be processed by the SGX enclave by sending the equivalent amount of native BTC back to the user’s wallet on Bitcoin
Learn more about the technology behind the bridge: