diff --git a/src/interfaces/IFeedOracle.sol b/src/interfaces/IFeedOracle.sol
deleted file mode 100644
index 5fa5851..0000000
--- a/src/interfaces/IFeedOracle.sol
+++ /dev/null
@@ -1,22 +0,0 @@
-// This file is part of Darwinia.
-// Copyright (C) 2018-2023 Darwinia Network
-// SPDX-License-Identifier: GPL-3.0
-//
-// Darwinia is free software: you can redistribute it and/or modify
-// it under the terms of the GNU General Public License as published by
-// the Free Software Foundation, either version 3 of the License, or
-// (at your option) any later version.
-//
-// Darwinia is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-// GNU General Public License for more details.
-//
-// You should have received a copy of the GNU General Public License
-// along with Darwinia. If not, see <https://www.gnu.org/licenses/>.
-
-pragma solidity 0.8.17;
-
-interface IFeedOracle {
-    function messageRootOf(uint256 chainid) external view returns (bytes32);
-}
diff --git a/src/interfaces/IORMP.sol b/src/interfaces/IORMP.sol
index e3a65ba..f2b12de 100644
--- a/src/interfaces/IORMP.sol
+++ b/src/interfaces/IORMP.sol
@@ -53,9 +53,7 @@ interface IORMP {
     /// @param message Verified receive message info.
     /// @param proof Message proof of this message.
     /// @return dispatchResult Result of the message dispatch.
-    function recv(Message calldata message, bytes calldata proof) external returns (bool dispatchResult);
-
-    function prove() external view returns (bytes32[32] memory);
+    function recv(Message calldata message, bytes calldata proof) external payable returns (bool dispatchResult);
 
     /// @dev Fetch user application config.
     /// @notice If user application has not configured, then the default config is used.
diff --git a/src/security/ExcessivelySafeCall.sol b/src/security/ExcessivelySafeCall.sol
index a1d6518..6b953a3 100644
--- a/src/security/ExcessivelySafeCall.sol
+++ b/src/security/ExcessivelySafeCall.sol
@@ -4,8 +4,6 @@ pragma solidity 0.8.17;
 // Inspired: https://github.com/LayerZero-Labs/solidity-examples/blob/main/contracts/util/ExcessivelySafeCall.sol
 
 library ExcessivelySafeCall {
-    uint256 private constant LOW_28_MASK = 0x00000000ffffffffffffffffffffffffffffffffffffffffffffffffffffffff;
-
     /// @notice Use when you _really_ really _really_ don't trust the called
     /// contract. This prevents the called contract from causing reversion of
     /// the caller in as many ways as we can.
@@ -104,25 +102,4 @@ library ExcessivelySafeCall {
         }
         return (_success, _returnData);
     }
-
-    /// @notice Swaps function selectors in encoded contract calls
-    /// @dev Allows reuse of encoded calldata for functions with identical
-    /// argument types but different names. It simply swaps out the first 4 bytes
-    /// for the new selector. This function modifies memory in place, and should
-    /// only be used with caution.
-    /// @param _newSelector The new 4-byte selector
-    /// @param _buf The encoded contract args
-    function swapSelector(bytes4 _newSelector, bytes memory _buf) internal pure {
-        require(_buf.length >= 4);
-        uint256 _mask = LOW_28_MASK;
-        assembly ("memory-safe") {
-            // load the first word of
-            let _word := mload(add(_buf, 0x20))
-            // mask out the top 4 bytes
-            // /x
-            _word := and(_word, _mask)
-            _word := or(_newSelector, _word)
-            mstore(add(_buf, 0x20), _word)
-        }
-    }
 }