How to hash Data/feed files for File transfers(sftp) using C#.net and Sqlsever 2014(Cryptography).

Microsoft .Net framework provided cryptography class object, These objects are usefully for encryption/decryption/hashing on sensitivity data files.(File transfers).

In the FTP world, Every organization transfer files to third party in a secure way using sftp protocols  with pgp /custom encryption  on data files.

Why Hash?

• Hash plays a role in security systems where they're used to ensure that transmitted data files have not been tampered by hacker.
• The sender generates a hash of the data file, encrypts it, and sends it with the Data file itself. 
• The recipient then decrypts both the Data File and the hash, 
• Recipient produces another hash from the received data file and compare sender hash and recipient generated hash
• If they're the same, there is a very high probability that the message was transmitted intact.

For demo purpose I have created a console application in C#.net using System.Security.Cryptography class and  Tsql scripts in SQL Server 2014 

Algorithm : SHA256

Demo

Step1:

A text file is created under C:\Hari\hari.txt and added "I am a good boy" as text.

Process generated hash on hari.txt file 

-- hash value with original value text ("I am a good boy")

F8C5F1FF1157F91FF64D1EFCA65B0A0318E84A21F72C3A6F5571E186A1D49D34

Step2:

next I opened  file C:\Hari\hari.txt and modified text inside "I am good boy, I am from Jamaica".

process generated hash on hari.txt file

-- hash value is changed when i modified a text file.

EC90609F3C3A58CA5DD499EB6833C4D66DA60E216A5A67BD9AAAFEB7133F6969

Step3:

when I compare both hash values, They did not match and possible tamper in the file.

the following code will give you an idea, How to generate hash.

Please find C# demo code here

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Security.Cryptography;

using System.IO;

namespace ConsoleApplication1

{

    class Program

    {

        static void Main(string[] args)

        {

            //hash some test file

            string path = @"C:\hari\hari.txt";

            string checksumMd5 = GetChecksum(path, Algorithms.MD5);

            string checksumSha1 = GetChecksum(path, Algorithms.SHA1);

            string checksumSha256 = GetChecksum(path, Algorithms.SHA256);

            string checksumSha384 = GetChecksum(path, Algorithms.SHA384);

            string checksumSha512 = GetChecksum(path, Algorithms.SHA512);

            string checksumRipemd160 = GetChecksum(path, Algorithms.RIPEMD160);

            //print buffer value.

            Console.Write(checksumSha256);

            //wait for userinput

            Console.ReadKey();

  

        }

        //  create algorithm class

        public static class Algorithms

        {

            public static readonly HashAlgorithm MD5 = new MD5CryptoServiceProvider();

            public static readonly HashAlgorithm SHA1 = new SHA1Managed();

            public static readonly HashAlgorithm SHA256 = new SHA256Managed();

            public static readonly HashAlgorithm SHA384 = new SHA384Managed();

            public static readonly HashAlgorithm SHA512 = new SHA512Managed();

            public static readonly HashAlgorithm RIPEMD160 = new RIPEMD160Managed();

        }

      // hashing file by reading data in the file using stream readers

        public static string GetChecksum(string filePath, HashAlgorithm algorithm)

        {

            using (var stream = new BufferedStream(File.OpenRead(filePath), 100000))

            {

                byte[] hash = algorithm.ComputeHash(stream);

                return BitConverter.ToString(hash).Replace("-", String.Empty);

            }

        }

    }

}

T sql script in Sql sever 2014.

I used Binary_check sum and Hash functions.