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Exercise 2

Transfer BTC to Ethereum (as a wrapped asset) and back using c2d2cli.

C2D2 is the axelar cross-chain dapp deamon which coordinates the necessary transactions for cross-chain asset transfers. The C2D2 CLI automates the steps we performed manually in exercise 1.

Status#

Work in progress.

Level#

Intermediate

Disclaimer#

warning

Axelar Network is a work in progress. At no point in time should you transfer any real assets using Axelar. Only use testnet tokens that you're not afraid to lose. Axelar is not responsible for any assets lost, frozen, or unrecoverable in any state or condition. If you find a problem, please submit an issue to this repository following the template.

Prerequisites#

  • Complete all steps from Setup

Useful links#

What you need#

Joining the Axelar testnet#

Follow the instructions in Setup to make sure your node is synchronized to the latest block, and you have received some test coins to your validator account.

Pull and enter the c2d2cli container#

Check Testnet Release for the latest available C2D2 version of the docker images.

On a new terminal window, enter the c2d2cli container by running:

./c2d2/c2d2cli.sh --version VERSION

Generate a key on Axelar and get some test tokens#

Create c2d2's Axelar blockchain account

c2d2cli keys add c2d2

Go to axelar faucet and fund your C2D2 account by providing the address to the facuet. You can get c2d2's account address by running 

c2d2cli keys show c2d2 -a

Fund your ethereum sender account#

Add an ethereum account to c2d2cli. When prompted enter the password passwordpassword.

c2d2cli bridge evm accounts add ethereum

You will be asked to enter a password for the account. Make a note of your password.

If you used a different password than passwordpassword you will need to either:

  1. enter your password manually during the transfer procedure
  2. Or provide your password to each c2d2cli command by adding the flag --evm-passphrase YOUR_PASSWORD
  3. Or configure your password by editing the /root/.c2d2cli/config.toml file.
  • Change the value in the sender-passphrase= key to your password.

List C2D2's accounts:

c2d2cli bridge evm accounts list ethereum

Account index 0 (the first address in the list) will be used to send transactions. Go to https://faucet.ropsten.be/ to get some Ropsten ETH for the sender account.

Mint ERC20 Bitcoin tokens on Ethereum#

  1. Generate a Bitcoin deposit address. For this step you will need to supply an Ethereum address that you have the private key for. This will be the [ethereum recipient address] in the example command below. This address will then be linked to the Bitcoin deposit address generated and will receive the pegged bitcoin (Satoshi tokens) on the Ethereum testnet.
c2d2cli transfer satoshi [ethereum recipient address] --source-chain bitcoin --dest-chain ethereum --gas=auto --gas-adjustment=1.4

You will see the deposit Bitcoin address printed in the terminal

action:  (2/7) Please deposit Bitcoin to tb1qgfk6v2ut9flwwkraj6t3syvpq22g0xhh2m73atfe79jv3msjwvzqtpuvfc
  1. External: send some TEST BTC on Bitcoin testnet to the deposit address specific above, and wait for 6 confirmations (i.e. the transaction is 6 blocks deep in the Bitcoin chain).

Do not exit c2d2cli while you are waiting for your deposit to be confirmed. It will be watching the bitcoin blockchain to detect your transaction.

  • If c2d2cli crashes or is closed during this step you can re-run the deposit-btc command with the same recipient address to resume.
  • If your transaction has 6 confirmations but c2d2cli has not detected it, you can restart c2d2cli and append the --bitcoin-tx-prompt flag.
  • The CLI will prompt you to enter the deposit tx info manually. The rest of the deposit procedure will still be automated.
  • c2d2cli transfer satoshi [ethereum recipient address] --source-chain bitcoin --dest-chain ethereum --bitcoin-tx-prompt --gas=auto --gas-adjustment=1.4

Once your transaction is detected, c2d2cli will wait until it has 6 confirmations before proceeding.

  1. C2D2 will automate the bitcoin deposit confirmation, and mint command signing and sending. Once the minting process completes you will see the following message:
Transferred satoshi to Ethereum address [ethereum recipient address]

You can now open Metamask and add the wrapped BTC contract address. c2d2cli will print the contract address like this:

Using AxelarGateway <address>Using satoshi token <address>

The contract will show in metamask as symbol 'Satoshi'. If your recipient address is in metamask, you will have an amount of satoshi tokens in metamask equal to your bitcoin deposit.

Burn ERC20 wrapped Bitcoin tokens and obtain native Satoshi#

  1. Generate an ethereum withdrawal address. The Bitcoin address you provide will be uniquely linked to the deposit address and receive the withdrawn BTC on the Bitcoin testnet. 
c2d2cli transfer satoshi [bitcoin recipient address] --source-chain ethereum --dest-chain bitcoin --gas=auto --gas-adjustment=1.4

For example:

c2d2cli transfer satoshi tb1qwtrclv55yy26awl2n40u57uck5xgty4w4h9eww --source-chain ethereum --dest-chain bitcoin --gas=auto --gas-adjustment=1.4

You will see the deposit Ethereum address printed in the terminal.

action:  (2/5) Please transfer satoshi tokens to Ethereum address 0xf5fccEeF24358fE24C53c1963d5d497BCD3ddF48 | ✓ Waiting for a withdrawal transaction
  1. External: send wrapped Satoshi tokens to withdrawal address (e.g. with Metamask). You need to have some Ropsten testnet Ether on the address to send transactions.
  1. Once your withdrawal transaction is detected, c2d2cli will wait for 30 Ropsten block confirmations before proceeding.

  1. c2d2cli will automate the withdrawal confirmation, and satoshi token (wrapped BTC) burning.

  2. Once your Satoshi tokens have been burned, you will see this message:

Transferred 5000 satoshi tokens to Bitcoin address [bitcoin recipient address]
  1. Your withdrawn BTC will be spendable by your recipient address once Bitcoin withdrawal consolidation occurs. Consolidation will be completed by a separate process.

An automated service processes all pending transfers from the Axelar network to Bitcoin a few times a day. Come back 24 hours to check your coins at the destination Bitcoin address on the testnet.

note

If your local axelar node fails, meaning c2d2cli cannot connect to it to broadcast transactions, you may use an Axelar public node to broadcast transactions by adding the config file flag --conf /config.testnet.toml like so:

c2d2cli transfer satoshi [bitcoin recipient address] --source-chain ethereum --dest-chain bitcoin --conf /config.testnet.toml --gas=auto --gas-adjustment=1.4