Design Cardano USDC minting policy

[serejke]

Overview

USDC on Cardano is a mint/burn token:

• when a Khalani protocol message (authorized by ISM) from Khalani chain hits Cardano, N USDC tokens must be minted to a recipient address
• when user exits Cardano, the USDC token gets burned and a Khalani protocol message to Khalani chain gets dispatched in the same transaction

Task

This task is to design the USDC minting policy taking into account Khalani protocol mechanics and necessary off-chain infrastructure.

[hai-kreate]

Here are the steps needed to implement this USDC minting policy:

• Implement an Inbox script: Reject duplicate inbound messages #50 (comment).
• Parameterize the multi-sig ISM with the Inbox script and requires a nonce check & update when issuing an authentic message.
• Allow burning the authentic token (when consumed) in the ISM minting policy.
• Implement the USDC minting policy parameterized by a multi-sig ISM (Khalani's in this case). A mint must burn an authentic message with the minting number read from the burned message. A burn is always accepted.
• (Optional) Parameterize the USDC minting policy with the Outbox script and requires a burn transaction to dispatch a valid message to the Outbox.

Note that we can share the minting policy for any wrapped token by reading the token name (USDC, USDT, etc.) from the (authentic) message body.

[hai-kreate]

Done for now!

• Minting Policy: https://github.com/tvl-labs/hyperlane-cardano/blob/main/src/onchain/mpKhalaniTokens.hl
• Message Recipient Script: https://github.com/tvl-labs/hyperlane-cardano/blob/main/src/onchain/scriptKhalani.hl
• Tests are implemented in both inbox & outbox.