github.com/fibonacci-chain/fbc@v0.0.0-20231124064014-c7636198c1e9/libs/cosmos-sdk/x/supply/spec/01_concepts.md (about)

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     4  
     5  # Concepts
     6  
     7  ## Supply
     8  
     9  The `supply` module:
    10  
    11  - passively tracks the total supply of coins within a chain,
    12  - provides a pattern for modules to hold/interact with `Coins`, and
    13  - introduces the invariant check to verify a chain's total supply.
    14  
    15  ### Total Supply
    16  
    17  The total `Supply` of the network is equal to the sum of all coins from the
    18  account. The total supply is updated every time a `Coin` is minted (eg: as part
    19  of the inflation mechanism) or burned (eg: due to slashing or if a governance
    20  proposal is vetoed).
    21  
    22  ## Module Accounts
    23  
    24  The supply module introduces a new type of `auth.Account` which can be used by
    25  modules to allocate tokens and in special cases mint or burn tokens.  At a base
    26  level these module accounts are capable of sending/receiving tokens to and from
    27  `auth.Account`s and other module accounts.  This design replaces previous
    28  alternative designs where, to hold tokens, modules would burn the incoming
    29  tokens from the sender account, and then track those tokens internally. Later,
    30  in order to send tokens, the module would need to effectively mint tokens
    31  within a destination account. The new design removes duplicate logic between
    32  modules to perform this accounting.
    33  
    34  The `ModuleAccount` interface is defined as follows:
    35  
    36  ```go
    37  type ModuleAccount interface {
    38    auth.Account               // same methods as the Account interface
    39    GetName() string           // name of the module; used to obtain the address
    40    GetPermissions() []string  // permissions of module account
    41    HasPermission(string) bool
    42  }
    43  ```
    44  
    45  > **WARNING!**
    46  Any module or message handler that allows either direct or indirect sending of funds must explicitly guarantee those funds cannot be sent to module accounts (unless allowed).
    47  
    48  The supply `Keeper` also introduces new wrapper functions for the auth `Keeper`
    49  and the bank `Keeper` that are related to `ModuleAccount`s in order to be able
    50  to:
    51  
    52  - Get and set `ModuleAccount`s by providing the `Name`.
    53  - Send coins from and to other `ModuleAccount`s or standard `Account`s
    54    (`BaseAccount` or `VestingAccount`) by passing only the `Name`.
    55  - `Mint` or `Burn` coins for a `ModuleAccount` (restricted to its permissions).
    56  
    57  ### Permissions
    58  
    59  Each `ModuleAccount` has a different set of permissions that provide different
    60  object capabilities to perform certain actions. Permissions need to be
    61  registered upon the creation of the supply `Keeper` so that every time a
    62  `ModuleAccount` calls the allowed functions, the `Keeper` can lookup the
    63  permissions to that specific account and perform or not the action.
    64  
    65  The available permissions are:
    66  
    67  - `Minter`: allows for a module to mint a specific amount of coins.
    68  - `Burner`: allows for a module to burn a specific amount of coins.
    69  - `Staking`: allows for a module to delegate and undelegate a specific amount of coins.