HMACSHA256 Hash key generated by C++/CLI is different from Java Generated Hash Key

Question

C++/CLI Function

I am generating Hash key using C++/CLI and Sending Data and Hashkey Over the network to Other Application which is coded in Java.

But Java Application generates a different HashKey.

Is it due to different applications on different servers that the hashkeys are different ?

Any Idea where am i going wrong ?

Thanking in Advance.

 char* EncodeData(char* ap_key, char*  ap_sourceData)
     {
        char* lp_data_to_send = NULL;
        int key_len = strlen(ap_key);

        String^ lv_data = gcnew String(ap_sourceData);//Getting Data in System String
        array<Byte>^ lv_main_data   = Encoding::UTF8->GetBytes(lv_data);//Encoding to UTF-8

        array<Byte>^key = gcnew array< Byte >(key_len + 2);
        Marshal::Copy((IntPtr)ap_key, key, 0, key_len); //Copy key in System Array Byte

        // Initialize the keyed hash object.
        HMACSHA256^ myhmacsha256 = gcnew HMACSHA256(key);

        // Compute the hash of the input file.
        array<Byte>^hashValue = myhmacsha256->ComputeHash(lv_main_data);

        String^ lv_hex_convert = BitConverter::ToString(hashValue)->Replace("-","");    //Converted to Hexadecimal and replacing '-' with ""
        Console::WriteLine(lv_hex_convert);//Converted Hexadecimal Hashkey

           //Converting to Char*
            lp_data_to_send = (char*)(void*)System::Runtime::InteropServices::Marshal::StringToHGlobalAnsi(lv_hex_convert);//Converting again to char* to be send to Calling Function

          myhmacsha256->Clear(); //myhmacsha256 clear Instance
          return lp_data_to_send;//Return Char*
    }


int main()
            {
                //Secret Key shared by C++/CLi application and Java Application
                String ^ lv_key_g = " My Secret Key";
                char lv_sourceData[] = { "My data" };
                char lv_destinationData[512] = { "" };
                char* lp_ret = NULL;

                array<Byte>^secretkey = gcnew array<Byte>(65); //Declaring Array
                //Converting to UTF-8 
                secretkey = Encoding::UTF8->GetBytes(lv_key_g);

                /*Converting to char* */

                pin_ptr<System::Byte> p = &secretkey[0];
                unsigned char* pby = p;
                //Converting to Char* to send
                char* lp_key = reinterpret_cast<char*>(pby);//Converting data to char* 

                /*End converting to Byte Array*/

                lp_ret = EncodeData(lp_key, lv_sourceData);//calling Function
            }

JAVA-FUNCTION

                String key = "My Key";      //Hash Key Shared by Both Application
                String hashKey = "My Data"; //Data Shared by both Application 
                Mac sha256_HMAC = null;
                try {
                    //Creating Instance
                    sha256_HMAC = Mac.getInstance("HmacSHA256");
                } catch (NoSuchAlgorithmException e) {
                    e.printStackTrace();
                }
                SecretKeySpec secret_key = null;
                try {

                    secret_key = new SecretKeySpec(key.getBytes("UTF-8"), "HmacSHA256");//UTF-8 Secret Key
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                }
                try {
                    sha256_HMAC.init(secret_key); //Init Secret Key
                } catch (InvalidKeyException e) {
                    e.printStackTrace();
                }
                final byte[] mac_data = sha256_HMAC.doFinal(hashKey.getBytes());  //Get Data in Bytes

                String result = "";
                for (final byte element : mac_data){
                //Using Radix 16 to convert to String
                        result += Integer.toString((element & 0xff) + 0x100, 16).substring(1);       //Converting to Hexadecimal
                    }
                    System.out.print(result);//Hashkey Print

Answer 1

return lp_data_to_send;//Return Char* will return a dangling pointer, you should probably return a reference-counted string lv_hex_convert instead. Another suspicious thing is that key is 2 bytes longer than required.