Anyone can mint aUSD using accepted reserve assets, and each aUSD is backed by a surplus value of reserve assets (collateral assets). The reserve assets are also cross-chain by nature, which can include Polkadot native assets (DOT and DOT derivatives), KSM and KSM derivatives like LKSM, Acala's native token ACA, and Karura's native token KAR. In the future, the protocol can also accept parachain assets and cross-chain assets like Bitcoin (BTC) and Ether (ETH) as collateral assets if they meet the risk requirements and are accepted via Acala governance.