diff --git a/contracts/interfaces/ISFC.sol b/contracts/interfaces/ISFC.sol
index c940a52..9a3f45a 100644
--- a/contracts/interfaces/ISFC.sol
+++ b/contracts/interfaces/ISFC.sol
@@ -121,6 +121,8 @@ interface ISFC {
 
     function getEpochEndBlock(uint256 epoch) external view returns (uint256);
 
+    function epochEndTime(uint256 epoch) external view returns (uint256);
+
     function rewardsStash(address delegator, uint256 validatorID) external view returns (uint256);
 
     function createValidator(bytes calldata pubkey) external payable;
diff --git a/contracts/sfc/SFC.sol b/contracts/sfc/SFC.sol
index 5b97ec3..f27501a 100644
--- a/contracts/sfc/SFC.sol
+++ b/contracts/sfc/SFC.sol
@@ -209,7 +209,7 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
     event AnnouncedRedirection(address indexed from, address indexed to);
 
     modifier onlyDriver() {
-        if (!isNode(msg.sender)) {
+        if (!_isNode(msg.sender)) {
             revert NotDriverAuth();
         }
         _;
@@ -552,6 +552,11 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
         return getEpochSnapshot[epoch].endBlock;
     }
 
+    /// Get epoch end time.
+    function epochEndTime(uint256 epoch) public view returns (uint256) {
+        return getEpochSnapshot[epoch].endTime;
+    }
+
     /// Check whether the given validator is slashed - the stake (or its part) cannot
     /// be withdrawn because of misbehavior (double-sign) of the validator.
     function isSlashed(uint256 validatorID) public view returns (bool) {
@@ -572,7 +577,7 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
     }
 
     /// Check if an address is the NodeDriverAuth contract.
-    function isNode(address addr) internal view virtual returns (bool) {
+    function _isNode(address addr) internal view virtual returns (bool) {
         return addr == address(node);
     }
 
@@ -649,7 +654,7 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
     }
 
     /// Get slashing penalty for a stake.
-    function getSlashingPenalty(
+    function _getSlashingPenalty(
         uint256 amount,
         bool isCheater,
         uint256 refundRatio
@@ -693,7 +698,7 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
 
         uint256 amount = getWithdrawalRequest[delegator][toValidatorID][wrID].amount;
         bool isCheater = isSlashed(toValidatorID);
-        uint256 penalty = getSlashingPenalty(amount, isCheater, slashingRefundRatio[toValidatorID]);
+        uint256 penalty = _getSlashingPenalty(amount, isCheater, slashingRefundRatio[toValidatorID]);
         delete getWithdrawalRequest[delegator][toValidatorID][wrID];
 
         if (amount <= penalty) {
@@ -777,11 +782,6 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
         }
     }
 
-    /// Get epoch end time.
-    function epochEndTime(uint256 epoch) internal view returns (uint256) {
-        return getEpochSnapshot[epoch].endTime;
-    }
-
     /// Check if an address is redirected.
     function _redirected(address addr) internal view returns (bool) {
         return getRedirection[addr] != address(0);
@@ -1045,6 +1045,22 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
         totalSupply = totalSupply + amount;
     }
 
+    /// Sync validator with node.
+    function _syncValidator(uint256 validatorID, bool syncPubkey) internal {
+        if (!_validatorExists(validatorID)) {
+            revert ValidatorNotExists();
+        }
+        // emit special log for node
+        uint256 weight = getValidator[validatorID].receivedStake;
+        if (getValidator[validatorID].status != OK_STATUS) {
+            weight = 0;
+        }
+        node.updateValidatorWeight(validatorID, weight);
+        if (syncPubkey && weight != 0) {
+            node.updateValidatorPubkey(validatorID, getValidatorPubkey[validatorID]);
+        }
+    }
+
     /// Notify stake subscriber about staking changes.
     /// Used to recount votes from delegators in the governance contract.
     function _notifyStakeSubscriber(address delegator, address validatorAuth, bool strict) internal {
@@ -1082,22 +1098,6 @@ contract SFC is OwnableUpgradeable, UUPSUpgradeable, Version {
         }
     }
 
-    /// Sync validator with node.
-    function _syncValidator(uint256 validatorID, bool syncPubkey) public {
-        if (!_validatorExists(validatorID)) {
-            revert ValidatorNotExists();
-        }
-        // emit special log for node
-        uint256 weight = getValidator[validatorID].receivedStake;
-        if (getValidator[validatorID].status != OK_STATUS) {
-            weight = 0;
-        }
-        node.updateValidatorWeight(validatorID, weight);
-        if (syncPubkey && weight != 0) {
-            node.updateValidatorPubkey(validatorID, getValidatorPubkey[validatorID]);
-        }
-    }
-
     /// Check if a validator exists.
     function _validatorExists(uint256 validatorID) internal view returns (bool) {
         return getValidator[validatorID].createdTime != 0;
diff --git a/contracts/test/UnitTestSFC.sol b/contracts/test/UnitTestSFC.sol
index e45a54d..5c40c05 100644
--- a/contracts/test/UnitTestSFC.sol
+++ b/contracts/test/UnitTestSFC.sol
@@ -40,11 +40,15 @@ contract UnitTestSFC is SFC {
         return time;
     }
 
-    function isNode(address addr) internal view override returns (bool) {
+    function _isNode(address addr) internal view override returns (bool) {
         if (allowedNonNodeCalls) {
             return true;
         }
-        return SFC.isNode(addr);
+        return SFC._isNode(addr);
+    }
+
+    function syncValidator(uint256 validatorID, bool syncPubkey) public {
+        _syncValidator(validatorID, syncPubkey);
     }
 }
 
diff --git a/test/SFC.ts b/test/SFC.ts
index c3351c3..e8e537d 100644
--- a/test/SFC.ts
+++ b/test/SFC.ts
@@ -65,7 +65,7 @@ describe('SFC', () => {
     });
 
     it('Should succeed and set genesis validator with bad status', async function () {
-      await this.sfc._syncValidator(1, false);
+      await this.sfc.syncValidator(1, false);
     });
 
     it('Should revert when sealEpoch not called by node', async function () {
@@ -946,7 +946,7 @@ describe('SFC', () => {
     });
 
     it('Should revert when syncing if validator does not exist', async function () {
-      await expect(this.sfc._syncValidator(33, false)).to.be.revertedWithCustomError(this.sfc, 'ValidatorNotExists');
+      await expect(this.sfc.syncValidator(33, false)).to.be.revertedWithCustomError(this.sfc, 'ValidatorNotExists');
     });
   });