Interacting with Cortado

Note: The Cortado testnet deployment will be frequently reset, thereby wiping out all user balances and history.

1. If not yet set up, install MetaMask and set up a new wallet.

2. In MetaMask, click on the upper left icon to select a network.

3. Click "Add network" -> "Add a network manually".

4. To interact with Vienna, the OP Stack rollup, add a network with these parameters:

   • Network name: Cortado Vienna

   • New RPC URL: https://vienna.calderachain.xyz/http

   • Chain ID: 0xc0ffee1

   • Block explorer URL: https://vienna.calderaexplorer.xyz

   • Currency symbol: SepoliaETH

5. To interact with the Polygon zkEVM stack rollup, add a network with these parameters:

   • Network name: Cortado Polygon

   • New RPC URL: https://polygon-preconfirmations.cortado.espresso.network

   • Chain ID: 0xc0ffee2

   For "Currency symbol", anything can be set (the native currency on the Polygon zkEVM stack rollup is a dummy testnet token produced by the faucet, and there is no bridge to SepoliaETH). "Block explorer URL" should be left blank.

Preconfirmations

The Espresso Sequencer uses the HotShot consensus protocol to provide fast confirmations of new blocks. These confirmations are secure, in that a block confirmed by HotShot is guaranteed to execute in the order determined by HotShot unless at least 1/3 of the total value staked in consensus is corrupt. They are also fast: a block may be confirmed by HotShot well before the same block is eventually processed by the layer 1 blockchain.

The RPC node for Cortado Polygon that you connected to above uses these "preconfirmations" from HotShot to achieve low latency, but there is a second RPC node that does not. In MetaMask, try going to Settings -> Networks -> Cortado Polygon and changing RPC URL to https://polygon.cortado.espresso.network. Then transfer some ETH on the Cortado Polygon network. Do you notice a difference in the speed with which the transaction gets confirmed?

For the Cortado testnet, the Vienna OP chain is only running a single RPC node, which does use preconfirmations, so you should experience low latency on the order of a few seconds there as well. However, note that MetaMask only refreshes pending transactions every 7 seconds. You may find it easier to observe low latency in the Vienna block explorer. Go to https://vienna.calderaexplorer.xyz/address/<address>, replacing <address> with your address in MetaMask. At the bottom you will see a section titled "Transactions", showing all the transactions made by this address. Now make a transfer in MetaMask on the Cortado Vienna network. How quickly does the new transaction appear in the block explorer?

Faucet

For the Cortado Vienna OP stack rollup, you can requests funds from the faucet. You can also directly deposit Sepolia ETH into the rollup using the Caldera bridge. Sepolia ETH can be obtained from the Sepolia faucet.

For the Polygon zkEVM stack rollup, you can request funds in the Discord #faucet channel with the following command: /faucet <address> To copy your MetaMask address, click on the address at the top of the MetaMask panel.