Imports System
Imports System.IO
Imports System.Security.Cryptography



Public Class MACTripleDESExample

    ' Computes a keyed hash for a source file, creates a target file with the keyed hash
    ' prepended to the contents of the source file, then decrypts the file and compares
    ' the source and the decrypted files.
    Public Shared Sub EncodeFile(ByVal key() As Byte, ByVal sourceFile As String, ByVal destFile As String) 
        ' Initialize the keyed hash object.
        Dim mac3Des As New MACTripleDES(key)
        Dim inStream As New FileStream(sourceFile, FileMode.Open)
        Dim outStream As New FileStream(destFile, FileMode.Create)
        ' Compute the hash of the input file.
        Dim hashValue As Byte() = mac3Des.ComputeHash(inStream)
        ' Reset inStream to the beginning of the file.
        inStream.Position = 0
        ' Write the computed hash value to the output file.
        outStream.Write(hashValue, 0, hashValue.Length)
        ' Copy the contents of the sourceFile to the destFile.
        Dim bytesRead As Integer
        ' read 1K at a time
        Dim buffer(1023) As Byte
        Do
            ' Read from the wrapping CryptoStream.
            bytesRead = inStream.Read(buffer, 0, 1024)
            outStream.Write(buffer, 0, bytesRead)
        Loop While bytesRead > 0
        mac3Des.Clear()
        ' Close the streams
        inStream.Close()
        outStream.Close()
        Return

    End Sub 'EncodeFile
     ' end EncodeFile

    ' Decrypt the encoded file and compare to original file.
    Public Shared Function DecodeFile(ByVal key() As Byte, ByVal sourceFile As String) As Boolean 
        ' Initialize the keyed hash object. 
        Dim mac3Des As New MACTripleDES(key)
        ' Create an array to hold the keyed hash value read from the file.
        Dim storedHash(mac3Des.HashSize / 8 - 1) As Byte
        ' Create a FileStream for the source file.
        Dim inStream As New FileStream(sourceFile, FileMode.Open)
        ' Read in the storedHash.
        inStream.Read(storedHash, 0, storedHash.Length)
        ' Compute the hash of the remaining contents of the file.
        ' The stream is properly positioned at the beginning of the content, 
        ' immediately after the stored hash value.
        Dim computedHash As Byte() = mac3Des.ComputeHash(inStream)
        ' compare the computed hash with the stored value
        Dim i As Integer
        For i = 0 To storedHash.Length - 1
            If computedHash(i) <> storedHash(i) Then
                Console.WriteLine("Hash values differ! Encoded file has been tampered with!")
                Return False
            End If
        Next i
        Console.WriteLine("Hash values agree -- no tampering occurred.")
        Return True

    End Function 'DecodeFile 'end DecodeFile
    Private Const usageText As String = "Usage: HMACSHA1 inputfile.txt encryptedfile.hsh" + vbLf + "You must specify the two file names. Only the first file must exist." + vbLf

    Public Shared Sub Main(ByVal Fileargs() As String) 

        Try
            ' Create a random key using a random number generator. This would be the
            '  secret key shared by sender and receiver.
            Dim secretkey() As Byte = New [Byte](23) {}
            'RNGCryptoServiceProvider is an implementation of a random number generator.
            Dim rng As New RNGCryptoServiceProvider()
            ' The array is now filled with cryptographically strong random bytes.
            rng.GetBytes(secretkey)

            ' Use the secret key to encode the message file.
            EncodeFile(secretkey, "Input.txt", "encryptedFile.hsh")

            ' Take the encoded file and decode
            DecodeFile(secretkey, "encryptedFile.hsh")
        Catch e As IOException
            Console.WriteLine("Error: File not found", e)
        End Try

    End Sub 'Main 
End Class 'MACTripleDESExample 'end main
'end class

using System;
using System.IO;
using System.Security.Cryptography;

public class MACTripleDESExample
{
    // Computes a keyed hash for a source file, creates a target file with the keyed hash
    // prepended to the contents of the source file, then decrypts the file and compares
    // the source and the decrypted files.
    public static void EncodeFile(byte[] key, String sourceFile, String destFile)
    {
        // Initialize the keyed hash object.
        MACTripleDES mac3Des = new MACTripleDES(key);
        FileStream inStream = new FileStream(sourceFile, FileMode.Open);
        FileStream outStream = new FileStream(destFile, FileMode.Create);
        // Compute the hash of the input file.
        byte[] hashValue = mac3Des.ComputeHash(inStream);
        // Reset inStream to the beginning of the file.
        inStream.Position = 0;
        // Write the computed hash value to the output file.
        outStream.Write(hashValue, 0, hashValue.Length);
        // Copy the contents of the sourceFile to the destFile.
        int bytesRead;
        // read 1K at a time
        byte[] buffer = new byte[1024];
        do
        {
            // Read from the wrapping CryptoStream.
            bytesRead = inStream.Read(buffer, 0, 1024);
            outStream.Write(buffer, 0, bytesRead);
        } while (bytesRead > 0);
        mac3Des.Clear();
        // Close the streams
        inStream.Close();
        outStream.Close();
        return;
    } // end EncodeFile


    // Decrypt the encoded file and compare to original file.
    public static bool DecodeFile(byte[] key, String sourceFile)
    {
        // Initialize the keyed hash object. 
        MACTripleDES mac3Des = new MACTripleDES(key);
        // Create an array to hold the keyed hash value read from the file.
        byte[] storedHash = new byte[mac3Des.HashSize / 8];
        // Create a FileStream for the source file.
        FileStream inStream = new FileStream(sourceFile, FileMode.Open);
        // Read in the storedHash.
        inStream.Read(storedHash, 0, storedHash.Length);
        // Compute the hash of the remaining contents of the file.
        // The stream is properly positioned at the beginning of the content, 
        // immediately after the stored hash value.
        byte[] computedHash = mac3Des.ComputeHash(inStream);
        // compare the computed hash with the stored value
        for (int i = 0; i < storedHash.Length; i++)
        {
            if (computedHash[i] != storedHash[i])
            {
                Console.WriteLine("Hash values differ! Encoded file has been tampered with!");
                return false;
            }
        }
        Console.WriteLine("Hash values agree -- no tampering occurred.");
        return true;
    } //end DecodeFile

    private const string usageText = "Usage: HMACSHA1 inputfile.txt encryptedfile.hsh\nYou must specify the two file names. Only the first file must exist.\n";
    public static void Main(string[] Fileargs)
    {

            try
            {
                // Create a random key using a random number generator. This would be the
                //  secret key shared by sender and receiver.
                byte[] secretkey = new Byte[24];
                //RNGCryptoServiceProvider is an implementation of a random number generator.
                RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider();
                // The array is now filled with cryptographically strong random bytes.
                rng.GetBytes(secretkey);

                // Use the secret key to encode the message file.
                EncodeFile(secretkey, "Input.txt", "encryptedFile.hsh");

                // Take the encoded file and decode
                DecodeFile(secretkey, "encryptedFile.hsh");
            }
            catch (IOException e)
            {
                Console.WriteLine("Error: File not found", e);
            }

    }  //end main
} //end class