Bank

Bank

Bank is a central component tracking Bitcoin balances. Balances can be transferred between balance owners, and balance owners can approve their balances to be spent by others. Balances in the Bank are updated for depositors who deposited their Bitcoin into the Bridge and only the Bridge can increase balances.

Bank is a governable contract and the Governance can upgrade the Bridge address.

bridge

address bridge

balanceOf

mapping(address => uint256) balanceOf

The balance of the given account in the Bank. Zero by default.

allowance

mapping(address => mapping(address => uint256)) allowance

The remaining amount of balance a spender will be allowed to transfer on behalf of an owner using transferBalanceFrom. Zero by default.

nonces

mapping(address => uint256) nonces

Returns the current nonce for an EIP2612 permission for the provided balance owner to protect against replay attacks. Used to construct an EIP2612 signature provided to the permit function.

cachedChainId

uint256 cachedChainId

cachedDomainSeparator

bytes32 cachedDomainSeparator

PERMIT_TYPEHASH

bytes32 PERMIT_TYPEHASH

Returns an EIP2612 Permit message hash. Used to construct an EIP2612 signature provided to the permit function.

BalanceTransferred

event BalanceTransferred(address from, address to, uint256 amount)

BalanceApproved

event BalanceApproved(address owner, address spender, uint256 amount)

BalanceIncreased

event BalanceIncreased(address owner, uint256 amount)

BalanceDecreased

event BalanceDecreased(address owner, uint256 amount)

BridgeUpdated

event BridgeUpdated(address newBridge)

onlyBridge

modifier onlyBridge()

constructor

constructor() public

updateBridge

function updateBridge(address _bridge) external

Allows the Governance to upgrade the Bridge address.

The function does not implement any governance delay and does not check the status of the Bridge. The Governance implementation needs to ensure all requirements for the upgrade are satisfied before executing this function. Requirements:

• The new Bridge address must not be zero.

Parameters

Name	Type	Description
_bridge	address	The new Bridge address.

transferBalance

function transferBalance(address recipient, uint256 amount) external

Moves the given amount of balance from the caller to recipient.

Requirements:

• recipient cannot be the zero address,

• the caller must have a balance of at least amount.

Parameters

Name	Type	Description
recipient	address	The recipient of the balance.
amount	uint256	The amount of the balance transferred.

approveBalance

function approveBalance(address spender, uint256 amount) external

Sets amount as the allowance of spender over the caller's balance. Does not allow updating an existing allowance to a value that is non-zero to avoid someone using both the old and the new allowance by unfortunate transaction ordering. To update an allowance to a non-zero value please set it to zero first or use increaseBalanceAllowance or decreaseBalanceAllowance for an atomic update.

If the amount is set to type(uint256).max, transferBalanceFrom will not reduce an allowance.

Parameters

Name	Type	Description
spender	address	The address that will be allowed to spend the balance.
amount	uint256	The amount the spender is allowed to spend.

approveBalanceAndCall

function approveBalanceAndCall(address spender, uint256 amount, bytes extraData) external

Sets the amount as an allowance of a smart contract spender over the caller's balance and calls the spender via receiveBalanceApproval.

If the amount is set to type(uint256).max, the potential transferBalanceFrom executed in receiveBalanceApproval of spender will not reduce an allowance. Beware that changing an allowance with this function brings the risk that spender may use both the old and the new allowance by unfortunate transaction ordering. Please use increaseBalanceAllowance and decreaseBalanceAllowance to eliminate the risk.

Parameters

Name	Type	Description
spender	address	The smart contract that will be allowed to spend the balance.
amount	uint256	The amount the spender contract is allowed to spend.
extraData	bytes	Extra data passed to the spender contract via receiveBalanceApproval call.

increaseBalanceAllowance

function increaseBalanceAllowance(address spender, uint256 addedValue) external

Atomically increases the caller's balance allowance granted to spender by the given addedValue.

Parameters

Name	Type	Description
spender	address	The spender address for which the allowance is increased.
addedValue	uint256	The amount by which the allowance is increased.

decreaseBalanceAllowance

function decreaseBalanceAllowance(address spender, uint256 subtractedValue) external

Atomically decreases the caller's balance allowance granted to spender by the given subtractedValue.

Requirements:

• spender must not be the zero address,

• the current allowance for spender must not be lower than the subtractedValue.

Parameters

Name	Type	Description
spender	address	The spender address for which the allowance is decreased.
subtractedValue	uint256	The amount by which the allowance is decreased.

transferBalanceFrom

function transferBalanceFrom(address spender, address recipient, uint256 amount) external

Moves amount of balance from spender to recipient using the allowance mechanism. amount is then deducted from the caller's allowance unless the allowance was made for type(uint256).max.

Requirements:

• recipient cannot be the zero address,

• spender must have a balance of at least amount,

• the caller must have an allowance for spender's balance of at least amount.

Parameters

Name	Type	Description
spender	address	The address from which the balance is transferred.
recipient	address	The address to which the balance is transferred.
amount	uint256	The amount of balance that is transferred.

permit

function permit(address owner, address spender, uint256 amount, uint256 deadline, uint8 v, bytes32 r, bytes32 s) external

An EIP2612 approval made with secp256k1 signature. Users can authorize a transfer of their balance with a signature conforming to the EIP712 standard, rather than an on-chain transaction from their address. Anyone can submit this signature on the user's behalf by calling the permit function, paying gas fees, and possibly performing other actions in the same transaction.

The deadline argument can be set to type(uint256).max to create permits that effectively never expire. If the amountis set totype(uint256).maxthentransferBalanceFromwill not reduce an allowance. Beware that changing an allowance with this function brings the risk that someone may use both the old and the new allowance by unfortunate transaction ordering. Please useincreaseBalanceAllowanceanddecreaseBalanceAllowance` to eliminate the risk.

Parameters

Name	Type	Description
owner	address	The balance owner who signed the permission.
spender	address	The address that will be allowed to spend the balance.
amount	uint256	The amount the spender is allowed to spend.
deadline	uint256	The UNIX time until which the permit is valid.
v	uint8	V part of the permit signature.
r	bytes32	R part of the permit signature.
s	bytes32	S part of the permit signature.

increaseBalances

function increaseBalances(address[] recipients, uint256[] amounts) external

Increases balances of the provided recipients by the provided amounts. Can only be called by the Bridge.

Requirements:

• length of recipients and amounts must be the same,

• none of recipients addresses must point to the Bank.

Parameters

Name	Type	Description
recipients	address[]	Balance increase recipients.
amounts	uint256[]	Amounts by which balances are increased.

increaseBalance

function increaseBalance(address recipient, uint256 amount) external

Increases balance of the provided recipient by the provided amount. Can only be called by the Bridge.

Requirements:

• recipient address must not point to the Bank.

Parameters

Name	Type	Description
recipient	address	Balance increase recipient.
amount	uint256	Amount by which the balance is increased.

increaseBalanceAndCall

function increaseBalanceAndCall(address vault, address[] recipients, uint256[] amounts) external

Increases the given smart contract vault's balance and notifies the vault contract about it. Can be called only by the Bridge.

Requirements:

• vault must implement IVault interface,

• length of recipients and amounts must be the same.

Parameters

Name	Type	Description
vault	address	Address of IVault recipient contract.
recipients	address[]	Balance increase recipients.
amounts	uint256[]	Amounts by which balances are increased.

decreaseBalance

function decreaseBalance(uint256 amount) external

Decreases caller's balance by the provided amount. There is no way to restore the balance so do not call this function unless you really know what you are doing!

Requirements:

• The caller must have a balance of at least amount.

Parameters

Name	Type	Description
amount	uint256	The amount by which the balance is decreased.

DOMAIN_SEPARATOR

function DOMAIN_SEPARATOR() public view returns (bytes32)

Returns hash of EIP712 Domain struct with TBTC Bank as a signing domain and Bank contract as a verifying contract. Used to construct an EIP2612 signature provided to the permit function.

_increaseBalance

function _increaseBalance(address recipient, uint256 amount) internal