Concepts

Cosmos-SDK Bank module Concepts

Supply

The supply functionality:

• passively tracks the total supply of coins within a chain,

• provides a pattern for modules to hold/interact with Coins, and

• introduces the invariant check to verify a chain's total supply.

Total Supply

The total Supply of the network is equal to the sum of all coins from the account. The total supply is updated every time a Coin is minted (eg: as part of the inflation mechanism) or burned (eg: due to slashing or if a governance proposal is vetoed).

Module Accounts

The supply functionality introduces a new type of auth.Account which can be used by modules to allocate tokens and in special cases mint or burn tokens. At a base level, these module accounts are capable of sending/receiving tokens to and from auth.Accounts and other module accounts. This design replaces previous alternative designs where to hold tokens, modules would burn the incoming tokens from the sender account, and then track those tokens internally. Later, in order to send tokens, the module would need to effectively mint tokens within a destination account. The new design removes duplicate logic between modules to perform this accounting.

Permissions

Each ModuleAccount has a different set of permissions that provide different object capabilities to perform certain actions. Permissions need to be registered upon the creation of the supply Keeper so that every time a ModuleAccount calls the allowed functions, the Keeper can look up the permissions to that specific account and perform or not the action.

The available permissions are:

• Minter: allows for a module to mint a specific amount of coins.

• Burner: allows for a module to burn a specific amount of coins.

• Staking: allows for a module to delegate and undelegate a specific amount of coins.