Zelana Bridge

The Zelana Bridge is a Solana-based program built using the Pinocchio. It enables the transfer of assets with a sequencer-based withdrawal mechanism, suggesting it is designed for integrations that require attested or privacy-preserving transactions.

Overview

The bridge operates on a simple yet powerful model:

• Initialization: A one-time setup to configure the bridge's operational parameters, including a trusted sequencer.
• Deposits: Users can deposit assets into a secure vault, and a receipt is generated on-chain to prove the transaction.
• Withdrawals: Withdrawals are processed by a trusted sequencer, which validates the request and authorizes the release of funds. This process uses a nullifier to prevent replay attacks and ensure that each withdrawal is unique.

How It Works

The bridge's functionality is divided into three main instructions:

1. Initialize: This instruction sets up the bridge by creating a Config account and a Vault account. The Config account stores essential parameters, such as the sequencer_authority, which is the public key of the trusted sequencer authorized to approve withdrawals. The Vault is a PDA that securely holds all deposited assets.

2. Deposit: When a user deposits assets, the process_deposit function transfers the funds into the Vault. It then creates a DepositReceipt account, which serves as an on-chain record of the deposit, containing details like the depositor's public key, the amount, a unique nonce, and a timestamp.

3. WithdrawAttested: The withdrawal process is managed by the process_withdraw_attested function and initiated by the sequencer. To withdraw funds, the sequencer provides a unique nullifier to prevent double-spending. The bridge verifies the sequencer's authority and then transfers the specified amount from the Vault to the recipient's account. A UsedNullifier account is created to ensure the same nullifier cannot be used again.

Accounts

The bridge uses the following on-chain accounts:

• Config: Stores the bridge's configuration, including the sequencer_authority and a domain identifier.
• Vault: A PDA that holds all deposited assets.
• DepositReceipt: A PDA created for each deposit, acting as a proof of the transaction.
• UsedNullifier: A PDA created for each withdrawal to mark a nullifier as used and prevent replay attacks.

Instructions

The program exposes the following instructions:

Instruction	Description	Accounts Required
Initialize	Initializes the bridge by creating the Config and Vault accounts.	payer, config_account, vault_account, system_program
Deposit	Deposits assets into the bridge and creates a DepositReceipt.	depositor, config_account, vault_account, deposit_receipt_account, system_program
WithdrawAttested	Withdraws assets from the bridge, authorized by the sequencer and using a unique nullifier.	sequencer, config_account, vault_account, recipient, user_nullifier_account, system_program

Client-Side Integration

The repository includes a gen-client.sh script, which is used to generate a client-side library for interacting with the on-chain program. The generated client can be found in the client/ directory.

To generate the client:

./gen-client.sh

Building and Testing

To build and test the program, you can use the following commands:

Build

cargo build-sbf

Test

cargo test

Program ID

The on-chain program ID for the Zelana Bridge is: 95sWqtU9fdm19cvQYu94iKijRuYAv3wLqod1pcsSfYth