Classe HMACSHA1 (System.Security.Cryptography)

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



Public Class HMACSHA1example

    ' 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 myhmacsha1 As New HMACSHA1(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() = myhmacsha1.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
        myhmacsha1.Clear()
        ' Close the streams
        inStream.Close()
        outStream.Close()
        Return

    End Sub


    ' 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 hmacsha1 As New HMACSHA1(key)
        ' Create an array to hold the keyed hash value read from the file.
        Dim storedHash(hmacsha1.HashSize / 8) 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() = hmacsha1.ComputeHash(inStream)
        ' compare the computed hash with the stored value
        Dim err As Boolean = False
        Dim i As Integer
        For i = 0 To storedHash.Length
            If computedHash(i) <> storedHash(i) Then
                Console.WriteLine("Hash values differ! Encoded file has been tampered with!")
                Return False
            End If
        Next i
        If (err) Then
            Console.WriteLine("Hash values differ! Encoded file has been tampered with!")
            Return False
        Else
            Console.WriteLine("Hash values agree -- no tampering occurred.")
            Return True
        End If
    End Function
    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)
        'If no file names are specified, write usage text.
        If Fileargs.Length < 2 Then
            Console.WriteLine(usageText)
        Else
            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](63) {}
                '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, Fileargs(0), Fileargs(1))

                ' Take the encoded file and decode
                DecodeFile(secretkey, Fileargs(1))
            Catch e As IOException
                Console.WriteLine("Error: File not found", e)
            End Try
        End If

    End Sub
End Class

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

public class HMACSHA1example
{
	// 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.
		HMACSHA1 myhmacsha1 = new HMACSHA1(key);
		FileStream inStream = new FileStream(sourceFile, FileMode.Open);
		FileStream outStream = new FileStream(destFile, FileMode.Create);
		// Compute the hash of the input file.
		byte[] hashValue = myhmacsha1.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); 
		myhmacsha1.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. 
		HMACSHA1 hmacsha1 = new HMACSHA1(key);
		// Create an array to hold the keyed hash value read from the file.
		byte[] storedHash = new byte[hmacsha1.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 = hmacsha1.ComputeHash(inStream);
		// compare the computed hash with the stored value
        bool err = false;
        for (int i = 0; i < storedHash.Length; i++)
        {
            if (computedHash[i] != storedHash[i])
            {
                err = true;
            }
        }
        if (err)
        {
            Console.WriteLine("Hash values differ! Encoded file has been tampered with!");
            return false;
        }
        else
        {
            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)
	{
		//If no file names are specified, write usage text.
		if (Fileargs.Length < 2)
		{
			Console.WriteLine(usageText);
		}
		else
		{
			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[64];
				//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, Fileargs[0], Fileargs[1]);

				// Take the encoded file and decode
				DecodeFile(secretkey, Fileargs[1]);
			}
			catch (IOException e)
			{
				Console.WriteLine("Error: File not found",e);
			}
		} //end if-else

	}  //end main
} //end class

using namespace System;
using namespace System::IO;
using namespace System::Security::Cryptography;

// 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.
void EncodeFile( array<Byte>^key, String^ sourceFile, String^ destFile )
{

   // Initialize the keyed hash object.
   HMACSHA1^ myhmacsha1 = gcnew HMACSHA1( key );
   FileStream^ inStream = gcnew FileStream( sourceFile,FileMode::Open );
   FileStream^ outStream = gcnew FileStream( destFile,FileMode::Create );

   // Compute the hash of the input file.
   array<Byte>^hashValue = myhmacsha1->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
   array<Byte>^buffer = gcnew array<Byte>(1024);
   do
   {

      // Read from the wrapping CryptoStream.
      bytesRead = inStream->Read( buffer, 0, 1024 );
      outStream->Write( buffer, 0, bytesRead );
   }
   while ( bytesRead > 0 );

   myhmacsha1->Clear();

   // Close the streams
   inStream->Close();
   outStream->Close();
   return;
} // end EncodeFile



// Decrypt the encoded file and compare to original file.
bool DecodeFile( array<Byte>^key, String^ sourceFile )
{

   // Initialize the keyed hash object. 
   HMACSHA1^ hmacsha1 = gcnew HMACSHA1( key );

   // Create an array to hold the keyed hash value read from the file.
   array<Byte>^storedHash = gcnew array<Byte>(hmacsha1->HashSize / 8);

   // Create a FileStream for the source file.
   FileStream^ inStream = gcnew 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.
   array<Byte>^computedHash = hmacsha1->ComputeHash( inStream );

   // compare the computed hash with the stored value
   bool err = false;
   for ( int i = 0; i < storedHash->Length; i++ )
   {
      if ( computedHash[ i ] != storedHash[ i ] )
      {
         err = true;
      }
   }
   if (err)
        {
            Console::WriteLine("Hash values differ! Encoded file has been tampered with!");
            return false;
        }
        else
        {
            Console::WriteLine("Hash values agree -- no tampering occurred.");
            return true;
        }

} //end DecodeFile


int main()
{
   array<String^>^Fileargs = Environment::GetCommandLineArgs();
   String^ usageText = "Usage: HMACSHA1 inputfile.txt encryptedfile.hsh\nYou must specify the two file names. Only the first file must exist.\n";

   //If no file names are specified, write usage text.
   if ( Fileargs->Length < 3 )
   {
      Console::WriteLine( usageText );
   }
   else
   {
      try
      {

         // Create a random key using a random number generator. This would be the
         //  secret key shared by sender and receiver.
         array<Byte>^secretkey = gcnew array<Byte>(64);

         //RNGCryptoServiceProvider is an implementation of a random number generator.
         RNGCryptoServiceProvider^ rng = gcnew 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, Fileargs[ 1 ], Fileargs[ 2 ] );

         // Take the encoded file and decode
         DecodeFile( secretkey, Fileargs[ 2 ] );
      }
      catch ( IOException^ e ) 
      {
         Console::WriteLine( "Error: File not found", e );
      }

   }
} //end main