Refresh the minimum bondable value

solidity/contracts/deposit/Deposit.sol

@@ -582,8 +582,6 @@ contract Deposit is DepositFactoryAuthority {
     ///        `FeeRebateToken`.
     /// @param _vendingMachineAddress `VendingMachine` address. More info in
     ///        `VendingMachine`.
-    /// @param _m Signing group honesty threshold.
-    /// @param _n Signing group size.
     /// @param _lotSizeSatoshis The minimum amount of satoshi the funder is
     ///                         required to send. This is also the amount of
     ///                         TBTC the TDT holder will be eligible to mint:
@@ -594,16 +592,14 @@ contract Deposit is DepositFactoryAuthority {
         IERC721 _tbtcDepositToken,
         FeeRebateToken _feeRebateToken,
         address _vendingMachineAddress,
-        uint16 _m,
-        uint16 _n,
         uint64 _lotSizeSatoshis
     ) public onlyFactory payable {
         self.tbtcSystem = _tbtcSystem;
         self.tbtcToken = _tbtcToken;
         self.tbtcDepositToken = _tbtcDepositToken;
         self.feeRebateToken = _feeRebateToken;
         self.vendingMachineAddress = _vendingMachineAddress;
-        self.initialize(_m, _n, _lotSizeSatoshis);
+        self.initialize(_lotSizeSatoshis);
     }
 
     /// @notice This function can only be called by the vending machine.

solidity/contracts/deposit/DepositFunding.sol

@@ -46,29 +46,21 @@ library DepositFunding {
     /// @dev If called directly, the transaction will revert since the call will
     ///      be executed on an already set-up instance.
     /// @param _d Deposit storage pointer.
-    /// @param _m Signing group honesty threshold.
-    /// @param _n Signing group size.
+    /// @param _lotSizeSatoshis Lot size in satoshis.
     function initialize(
         DepositUtils.Deposit storage _d,
-        uint16 _m,
-        uint16 _n,
         uint64 _lotSizeSatoshis
     ) public {
         require(_d.tbtcSystem.getAllowNewDeposits(), "New deposits aren't allowed.");
         require(_d.inStart(), "Deposit setup already requested");
-        require(_d.tbtcSystem.isAllowedLotSize(_lotSizeSatoshis), "provided lot size not supported");
 
         _d.lotSizeSatoshis = _lotSizeSatoshis;
-        uint256 _bondRequirementSatoshi = _lotSizeSatoshis.mul(_d.tbtcSystem.getInitialCollateralizedPercent()).div(100);
-        uint256 _bondRequirementWei = _d.fetchBitcoinPrice().mul(_bondRequirementSatoshi);
 
         _d.keepSetupFee = _d.tbtcSystem.getNewDepositFeeEstimate();
 
         /* solium-disable-next-line value-in-payable */
         _d.keepAddress = _d.tbtcSystem.requestNewKeep.value(msg.value)(
-            _m,
-            _n,
-            _bondRequirementWei,
+            _lotSizeSatoshis,
             TBTCConstants.getDepositTerm()
         );
 

solidity/contracts/interfaces/ITBTCSystem.sol

@@ -17,7 +17,7 @@ interface ITBTCSystem {
     function getNewDepositFeeEstimate() external view returns (uint256);
     function getAllowNewDeposits() external view returns (bool);
     function isAllowedLotSize(uint64 _lotSizeSatoshis) external view returns (bool);
-    function requestNewKeep(uint256 _m, uint256 _n, uint256 _bond, uint256 _maxSecuredLifetime) external payable returns (address);
+    function requestNewKeep(uint64 _lotSizeSatoshis, uint256 _maxSecuredLifetime) external payable returns (address);
     function getSignerFeeDivisor() external view returns (uint16);
     function getInitialCollateralizedPercent() external view returns (uint16);
     function getUndercollateralizedThresholdPercent() external view returns (uint16);

solidity/contracts/proxy/DepositFactory.sol

@@ -25,8 +25,6 @@ contract DepositFactory is CloneFactory, TBTCSystemAuthority{
     TBTCToken public tbtcToken;
     FeeRebateToken public feeRebateToken;
     address public vendingMachineAddress;
-    uint16 public keepThreshold;
-    uint16 public keepSize;
 
     constructor(address _systemAddress)
         TBTCSystemAuthority(_systemAddress)
@@ -39,26 +37,20 @@ contract DepositFactory is CloneFactory, TBTCSystemAuthority{
     /// @param _tbtcDepositToken      TBTC Deposit Token contract.
     /// @param _feeRebateToken        AFee Rebate Token contract.
     /// @param _vendingMachineAddress Address of the Vending Machine contract.
-    /// @param _keepThreshold         Minimum number of honest keep members.
-    /// @param _keepSize              Number of all members in a keep.
     function setExternalDependencies(
         address payable _masterDepositAddress,
         TBTCSystem _tbtcSystem,
         TBTCToken _tbtcToken,
         TBTCDepositToken _tbtcDepositToken,
         FeeRebateToken _feeRebateToken,
-        address _vendingMachineAddress,
-        uint16 _keepThreshold,
-        uint16 _keepSize
+        address _vendingMachineAddress
     ) public onlyTbtcSystem {
         masterDepositAddress = _masterDepositAddress;
         tbtcDepositToken = _tbtcDepositToken;
         tbtcSystem = _tbtcSystem;
         tbtcToken = _tbtcToken;
         feeRebateToken = _feeRebateToken;
         vendingMachineAddress = _vendingMachineAddress;
-        keepThreshold = _keepThreshold;
-        keepSize = _keepSize;
     }
 
     event DepositCloneCreated(address depositCloneAddress);
@@ -87,8 +79,6 @@ contract DepositFactory is CloneFactory, TBTCSystemAuthority{
                 tbtcDepositToken,
                 feeRebateToken,
                 vendingMachineAddress,
-                keepThreshold,
-                keepSize,
                 _lotSizeSatoshis
             );
 

solidity/contracts/system/KeepFactorySelection.sol

@@ -49,7 +49,7 @@ library KeepFactorySelection {
     function initialize(
         Storage storage _self,
         IBondedECDSAKeepFactory _defaultFactory
-    ) internal {
+    ) public {
         require(
             address(_self.keepStakeFactory) == address(0),
             "Already initialized"
@@ -89,6 +89,34 @@ library KeepFactorySelection {
         return factory;
     }
 
+    /// @notice Sets the minimum bondable value required from the operator to
+    /// join the sortition pool for tBTC.
+    /// @param _minimumBondableValue The minimum bond value the application
+    /// requires from a single keep.
+    /// @param _groupSize Number of signers in the keep.
+    /// @param _honestThreshold Minimum number of honest keep signers.
+    function setMinimumBondableValue(
+        Storage storage _self,
+        uint256 _minimumBondableValue,
+        uint256 _groupSize,
+        uint256 _honestThreshold
+    ) public {
+        if (address(_self.keepStakeFactory) != address(0)) {
+            _self.keepStakeFactory.setMinimumBondableValue(
+                _minimumBondableValue,
+                _groupSize,
+                _honestThreshold
+            );
+        }
+        if (address(_self.ethStakeFactory) != address(0)) {
+            _self.ethStakeFactory.setMinimumBondableValue(
+                _minimumBondableValue,
+                _groupSize,
+                _honestThreshold
+            );
+        }
+    }
+
     /// @notice Refreshes the keep factory choice. If either ETH-stake factory
     /// or selection strategy is not set, KEEP-stake factory is selected.
     /// Otherwise, calls selection strategy providing addresses of both

solidity/contracts/system/TBTCSystem.sol

@@ -67,6 +67,9 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
 
     KeepFactorySelection.Storage keepFactorySelection;
 
+    uint16 public keepSize;
+    uint16 public keepThreshold;
+
     // Parameters governed by the TBTCSystem owner
     bool private allowNewDeposits = false;
     uint16 private signerFeeDivisor = 2000; // 1/2000 == 5bps == 0.05% == 0.0005
@@ -124,6 +127,8 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
         require(initializedTimestamp == 0, "already initialized");
 
         keepFactorySelection.initialize(_defaultKeepFactory);
+        keepThreshold = _keepThreshold;
+        keepSize = _keepSize;
 
         _vendingMachine.setExternalAddresses(
             _tbtcToken,
@@ -136,9 +141,7 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
             _tbtcToken,
             _tbtcDepositToken,
             _feeRebateToken,
-            address(_vendingMachine),
-            _keepThreshold,
-            _keepSize
+            address(_vendingMachine)
         );
         setTbtcDepositToken(_tbtcDepositToken);
         initializedTimestamp = block.timestamp;
@@ -151,16 +154,16 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
         return allowNewDeposits;
     }
 
+    /// @notice Return the lowest lot size currently enabled for deposits.
+    /// @return The lowest lot size, in satoshis.
+    function getMinimumLotSize() public view returns (uint256) {
+        return lotSizesSatoshis[0];
+    }
+
     /// @notice Return the largest lot size currently enabled for deposits.
     /// @return The largest lot size, in satoshis.
-    function getMaxLotSize() public view returns (uint256) {
-        uint256 max = 0;
-        for (uint i = 0; i<lotSizesSatoshis.length; i++) {
-            if (lotSizesSatoshis[i] > max) {
-                max = lotSizesSatoshis[i];
-            }
-        }
-        return max;
+    function getMaximumLotSize() public view returns (uint256) {
+        return lotSizesSatoshis[lotSizesSatoshis.length - 1];
     }
 
     /// @notice One-time-use emergency function to disallow future deposit creation for 10 days.
@@ -213,7 +216,8 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
     /// @notice Set the allowed deposit lot sizes.
     /// @dev    Lot size array should always contain 10**8 satoshis (1 BTC) and
     ///         cannot contain values less than 50000 satoshis (0.0005 BTC) or
-    ///         greater than 10**10 satoshis (100 BTC).
+    ///         greater than 10**10 satoshis (100 BTC). Lot size array must not
+    ///         have duplicates and it must be sorted.
     ///         This can be finalized by calling `finalizeLotSizesUpdate`
     ///         anytime after `governanceTimeDelay` has elapsed.
     /// @param _lotSizes Array of allowed lot sizes.
@@ -230,6 +234,10 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
             } else if (_lotSizes[i] > 10 * 10**9) {
                 // Failed the maximum requirement, break on out.
                 revert("Lot sizes greater than 100 BTC are not allowed");
+            } else if (i > 0 && _lotSizes[i] == _lotSizes[i-1]) {
+                revert("Lot size array must not have duplicates");
+            } else if (i > 0 && _lotSizes[i] < _lotSizes[i-1]) {
+                revert("Lot size array must be sorted");
             }
         }
 
@@ -377,6 +385,8 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
         emit LotSizesUpdated(newLotSizesSatoshis);
         lotSizesChangeInitiated = 0;
         newLotSizesSatoshis.length = 0;
+
+        refreshMinimumBondableValue();
     }
 
     /// @notice Finish setting the system collateralization levels
@@ -468,18 +478,6 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
         return lotSizesSatoshis;
     }
 
-    /// @notice Check if a lot size is allowed.
-    /// @param _lotSizeSatoshis Lot size to check.
-    /// @return True if lot size is allowed, false otherwise.
-    function isAllowedLotSize(uint64 _lotSizeSatoshis) external view returns (bool){
-        for( uint i = 0; i < lotSizesSatoshis.length; i++){
-            if (lotSizesSatoshis[i] == _lotSizeSatoshis){
-                return true;
-            }
-        }
-        return false;
-    }
-
     /// @notice Get the system undercollateralization level for new deposits
     function getUndercollateralizedThresholdPercent() external view returns (uint16) {
         return undercollateralizedThresholdPercent;
@@ -506,13 +504,7 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
             "Caller must be a Deposit contract"
         );
 
-        uint256 price = priceFeed.getPrice();
-        if (price == 0 || price > 10 ** 18) {
-            // This is if a sat is worth 0 wei, or is worth >1 ether. Revert at
-            // once.
-            revert("System returned a bad price");
-        }
-        return price;
+        return _fetchBitcoinPrice();
     }
 
     // Difficulty Oracle
@@ -566,6 +558,20 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
         );
     }
 
+    /// @notice Refreshes the minimum bondable value required from the operator
+    /// to join the sortition pool for tBTC. The minimum bondable value is
+    /// equal to the current minimum lot size collateralized 150% multiplied by
+    /// the current BTC price.
+    /// @dev It is recommended to call this function on tBTC initialization and
+    /// after minimum lot size update.
+    function refreshMinimumBondableValue() public {
+        keepFactorySelection.setMinimumBondableValue(
+            calculateBondRequirementWei(getMinimumLotSize()),
+            keepSize,
+            keepThreshold
+        );
+    }
+
     /// @notice Returns the time delay used for governance actions except for
     ///         price feed additions.
     function getGovernanceTimeDelay() public pure returns (uint256) {
@@ -590,23 +596,58 @@ contract TBTCSystem is Ownable, ITBTCSystem, DepositLog {
     }
 
     /// @notice Request a new keep opening.
-    /// @param _m Minimum number of honest keep members required to sign.
-    /// @param _n Number of members in the keep.
+    /// @param _lotSizeSatoshis Lot size in satoshis.
     /// @param _maxSecuredLifetime Duration of stake lock in seconds.
     /// @return Address of a new keep.
     function requestNewKeep(
-        uint256 _m,
-        uint256 _n,
-        uint256 _bond,
+        uint64 _lotSizeSatoshis,
         uint256 _maxSecuredLifetime
     )
         external
         payable
         returns (address)
     {
         require(tbtcDepositToken.exists(uint256(msg.sender)), "Caller must be a Deposit contract");
+        require(isAllowedLotSize(_lotSizeSatoshis), "provided lot size not supported");
+
         IBondedECDSAKeepFactory _keepFactory = keepFactorySelection.selectFactoryAndRefresh();
-        return _keepFactory.openKeep.value(msg.value)(_n, _m, msg.sender, _bond, _maxSecuredLifetime);
+        uint256 bond = calculateBondRequirementWei(_lotSizeSatoshis);
+        return _keepFactory.openKeep.value(msg.value)(keepSize, keepThreshold, msg.sender, bond, _maxSecuredLifetime);
+    }
+
+    /// @notice Check if a lot size is allowed.
+    /// @param _lotSizeSatoshis Lot size to check.
+    /// @return True if lot size is allowed, false otherwise.
+    function isAllowedLotSize(uint64 _lotSizeSatoshis) public view returns (bool){
+        for( uint i = 0; i < lotSizesSatoshis.length; i++){
+            if (lotSizesSatoshis[i] == _lotSizeSatoshis){
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /// @notice Calculates bond requirement in wei for the given lot size in
+    /// satoshis based on the current ETHBTC price.
+    /// @param _lotSizeSatoshis Lot size in satoshis.
+    /// @return Bond requirement in wei.
+    function calculateBondRequirementWei(
+        uint256 _lotSizeSatoshis
+    ) internal view returns (uint256) {
+        uint256 bondRequirementSatoshis = _lotSizeSatoshis.mul(
+            initialCollateralizedPercent
+        ).div(100);
+        return _fetchBitcoinPrice().mul(bondRequirementSatoshis);
+    }
+
+    function _fetchBitcoinPrice() internal view returns (uint256) {
+        uint256 price = priceFeed.getPrice();
+        if (price == 0 || price > 10 ** 18) {
+            // This is if a sat is worth 0 wei, or is worth >1 ether. Revert at
+            // once.
+            revert("System returned a bad price");
+        }
+        return price;
     }
 
     /// @notice Get the time remaining until the function parameter timer value can be updated.

solidity/contracts/test/deposit/TestDeposit.sol

@@ -18,16 +18,14 @@ contract TestDeposit is Deposit {
         IERC721 _tbtcDepositToken,
         FeeRebateToken _feeRebateToken,
         address _vendingMachineAddress,
-        uint16 _m,
-        uint16 _n,
         uint64 _lotSizeSatoshis
     ) public payable {
         self.tbtcSystem = _tbtcSystem;
         self.tbtcToken = _tbtcToken;
         self.tbtcDepositToken = _tbtcDepositToken;
         self.feeRebateToken = _feeRebateToken;
         self.vendingMachineAddress = _vendingMachineAddress;
-        self.initialize(_m, _n, _lotSizeSatoshis);
+        self.initialize(_lotSizeSatoshis);
     }
 
     function setExteriorAddresses(