Using Transfer Hooks

What are Transfer Hooks?

Aera transfer hooks exist to enable custom functionality during vault unit transfers such as whitelist/blacklist checks. Transfer hooks can embed arbitrary logic ranging from simple acceptance checks to more stateful logic such as rewards management.

Why They Matter?

Many vault owners need to enforce restrictions on who can receive vault units. This enables permissioned vaults or can be used to support a holistic compliance strategy.

How to Choose a Transfer Hook?

A vault transfer hook needs to implement a beforeTransfer function which accepts the from address, to address and the transferAgent. Two hooks are available to vault owners out-of-the-box: the TransferWhitelistHook and the TransferBlacklistHook.

The TransferWhitelistHook maintains a list of whitelisted addresses and only allows vault units to be sent to whitelisted addresses. The whitelist hook can be used in permissioned vaults with a fixed set of participants.

The TransferBlacklistHook can be configured with a blacklist oracle. It's compatible with the Chainalysis sanctions oracle interface but can be used with any custom blacklist.

Caveats

Hooks can be updated using setBeforeTransferHook.