How it works
ITS Hub
The contract on the Axelar network that every interchain transfer goes through.
The ITS Hub is a CosmWasm contract on the Axelar network. ITS on each chain doesn't send messages to ITS on other chains directly: every transfer, token deployment and token link goes through the hub, as two GMP messages.
- ITS on the source chain sends a message to the hub, with the destination chain and the ITS message inside (message type
SEND_TO_HUB,3). - The hub checks the message, updates its records and sends it to ITS on the destination chain, with the source chain and the ITS message inside (
RECEIVE_FROM_HUB,4).
On Axelarscan, a transfer therefore shows as two messages: one to the chain axelar, and one from it. The hub's address is axelar1aqcj54lzz0rk22gvqgcn8fr5tx4rzwdv5wv5j9dmnacgefvd7wzsy2j2mr on mainnet and testnet.
What the hub does
- Accepts only registered chains. Each chain's ITS contract is registered with the hub through Axelar governance. Messages from or to other addresses are rejected.
- Tracks supply. For tokens that only ITS can mint (no custom minter), the hub records how much of the token has been sent to each chain, and rejects transfers back from a chain of more than that amount. A compromised chain can't send back more than it received.
- Converts amounts between chains. Chains differ in how large an integer a token amount can be. When a token is deployed to a chain with a smaller maximum, the hub reduces its decimals there, and scales the amounts of transfers between chains accordingly.
- Translates messages. Each chain has a translator contract that converts its ITS messages to and from the hub's format: an ABI translator for most chains, and one for Solana's encoding.
- Can be paused. Axelar can freeze a chain in the hub, or stop all execution, in an emergency.
Flow limits aren't in the hub: each token's token manager enforces them on its chain. See Flow limits.