Transaction Optimistic Rollups

A Transaction Optimistic Rollup (TORU) is an experimental temporary scaling solution to help Tezos developers and users get acquainted with the idea of working with rollups.

This is a trimmed, more concise documentation of how to do TORU operations in Taquito. If you aren't yet familiar with rollup node interactions, please refer to this documentation by Nomadic Labs.

TORU currently supports the transferring of funds in the form of tickets. Fund (or ticket) transfers can be done from:

• Layer-1 to layer 2 (deposit)
• Layer-2 to layer 2 (transfer)
• Layer-2 to layer-1 (withdrawal)

Taquito currently supports layer-1 operations that facilitate deposits and withdrawals to and from the rollup node.

Deposits

To be able to interact or transfer funds on layer-2, you will first need to deposit an amount to an existing layer-2 (tz4) address.

Depositing tickets from layer-1 to layer-2 can be done via a smart contract that facilitates the transfer to a tz4 address in a specified rollup node.

An example of such contract can be found here

Assuming the contract has been originated, interacting with the contract in Taquito would look something like this:

const Tezos = new TezosToolkit('https://jakartanet.ecadinfra.com');

const deposit = Tezos.contract.at(SMART_CONTRACT_ADDRESS);

const op = await deposit.methods.default(
    'foobar',
    '15',
    'tz4Jxn8MpRndqWUzkuZbQKmE3aNWJzYsSEso',
    'txr1c9XcfmiLSWeqDPamPytns2ZXvwgYA7EpA'
);

const confirmation = await op.confirmation();

console.log(op.hash);
console.log(op.operationResults);

The default entrypoint takes in 4 arguments:

• foobar is the ticket string
• 15 is the quantity of a ticket string
• tz4Jxn8MpRndqWUzkuZbQKmE3aNWJzYsSEso is the layer-2 address that will be the deposit recipient
• txr1c9XcfmiLSWeqDPamPytns2ZXvwgYA7EpA is the rollup node id

If the deposit is successful, you will be returned an operation hash that can be accessed via op.hash

You also might want to look at op.operationResults to retrieve the ticket_hash. A ticket hash should look something like this: exprtz9FgfdzufUADVsvP8Gj8d8PZr9RsBEjZ5GQKM8Kp5cKWww7di

Transfer

The exchange of assets in the form of tickets can be done from a layer-2 (tz4) address to another layer-2 address. Not to be confused with the transfer_ticket operation, this layer-2 operation will not be supported in Taquito. This may change in the future with SCORU (Smart Contract Optimistic Rollups).

For instructions on how to conduct a transfer in layer-2 using the rollup client, refer to this documentation by Nomadic Labs.

Withdrawal

A withdrawal of assets from layer-2 back to layer-1 can be done in several steps.

The first step is to perform a withdraw in layer-2 to a layer-1 address in the rollup client.

tezos-tx-rollup-client-alpha withdraw ${qty} of ${ticket_hash} from ${l2_src} to ${l1_dst}

• ${qty} is the quantity of a ticket string that you would like to withdraw
• ${ticket_hash} is the ticket hash that was returned by a deposit
• ${l2_src} is the BLS pair of keys generated with tezos-client bls gen key; or in other words, the tz4 address that holds the tickets
• ${l1_dst} is the layer-1 address you would like to withdraw the tickets to

After a successful withdrawal, your assets will exist back in layer-1 in the form of tickets after the finality period ends.

danger

Please note that this first step is a layer-2 operation which Taquito does not currently support.

The second step is to use a Tezos operation that will transfer these tickets to a smart contract. You can use your own contracts to process the tickets as you'd like (e.g. allow access to XTZ existing in the tickets, etc).

This second step is called a Transfer Ticket operation, which Taquito supports.

const Tezos = new TezosToolkit('https://jakartanet.ecadinfra.com');

const op = await Tezos.contract.transferTicket({
    ticketContents: { "string": "foobar" },
    ticketTy: { "prim": "string" } ,
    ticketTicketer: 'KT1AL8we1Bfajn2M7i3gQM5PJEuyD36sXaYb',
    ticketAmount: 5,
    destination: KT1SUT2TBFPCknkBxLqM5eJZKoYVY6mB26Fg,
    entrypoint: 'default',
});

• ticket_amount is the amount that you would like to transfer to the smart contract
• destination is the address of the smart contract you would like to transfer the tickets to
• entrypoint is the entrypoint of the destination smart contract
• ticket_contents, ticket_ty, and ticket_ticketer can be retrieved from running this command using the rollup client (see documentation)

tezos-tx-rollup-client-alpha rpc get "/context/head/tickets/${ticket_hash}"

Glossary

• Layer-1 refers to our main protocol networks related to on-chain transactions
• Layer-2 refers to rollup nodes deployed by any individual/group to receive transactions off-chain
• TORU is short for Transactional Optimistic Rollup; the experimental, temporary introduction for rollup nodes
• SCORU is short for Smart Contract Optimistic Rollup; the more 'permanent' solution that has yet to be be released
• Finality Period refers to the number of blocks needed for the chain to finalize transactions on a rollup node (40,000 blocks on mainnet and testnets, 10 blocks on Mondaynet and Dailynet for ease of testing and demo purposes). See documentation.