Csharp/C Sharp/File Stream/File Cryptography

Illustrates asymmetric cryptography

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example19_11.cs illustrates asymmetric cryptography
*/
using System;
using System.IO;
using System.Security.Cryptography;
public class Example19_11 
{
    public static void Main() 
    {
        // Create a new crypto provider
        RSACryptoServiceProvider rsa = 
            new RSACryptoServiceProvider();
        // Data to encrypt
        Byte[] testData = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
        // Encrypt the data
        Byte[] encryptedData = rsa.Encrypt(testData, false);
        Console.WriteLine("Encrypted data:");
        for(int i=0; i<encryptedData.GetLength(0); i++)
        {
            Console.Write("{0} ", encryptedData[i]);
        }
        Console.WriteLine();
        // Decrypt the data
        Byte[] decryptedData = rsa.Decrypt(encryptedData, false);
        Console.WriteLine("Decrypted Data:");
        for(int i=0; i<decryptedData.GetLength(0); i++)
        {
            Console.Write("{0} ", decryptedData[i]);
        }
        Console.WriteLine();
    }
}

Illustrates declarative role-based security

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/

/*
  Example19_8.cs illustrates declarative role-based security
*/
using System;
using System.IO;
using System.Security.Permissions;
[PrincipalPermissionAttribute(SecurityAction.Demand, Role="Administrators")]
public class Example19_8 
{
    public static void Main() 
    {
        // Create a new file to work with
        FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
        // Create a StreamWriter to handle writing
        StreamWriter sw = new StreamWriter(fsOut);
        // And write some data
        sw.WriteLine(""Twas brillig, and the slithy toves");
        sw.WriteLine("Did gyre and gimble in the wabe.");
        sw.Flush();
        sw.Close();
    }
}

Illustrates decrypting a file

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example19_10.cs illustrates decrypting a file
*/
using System;
using System.IO;
using System.Security.Cryptography;
public class Example19_10 
{
    public static void Main() 
    {
        // Create a new crypto provider
        TripleDESCryptoServiceProvider tdes = 
            new TripleDESCryptoServiceProvider();
        // open the file containing the key and IV
        FileStream fsKeyIn = File.OpenRead(@"c:\temp\encrypted.key");
        
        // use a BinaryReader to read formatted data from the file
        BinaryReader br = new BinaryReader(fsKeyIn);
        // read data from the file and close it
        tdes.Key = br.ReadBytes(24);
        tdes.IV = br.ReadBytes(8);
        // Open the encrypted file
        FileStream fsIn = File.OpenRead(@"c:\\temp\\encrypted.txt");
        // Create a cryptostream to decrypt from the filestream
        CryptoStream cs = new CryptoStream(fsIn, tdes.CreateDecryptor(),
            CryptoStreamMode.Read);
        // Create a StreamReader to format the input
        StreamReader sr = new StreamReader(cs);
        // And decrypt the data
        Console.WriteLine(sr.ReadToEnd());
        sr.Close();
    }
}

Illustrates demanding permissions

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example19_5.cs illustrates demanding permissions
*/
using System;
using System.IO;
using System.Security.Permissions;
[FileIOPermissionAttribute(SecurityAction.Demand,
All=@"c:\\temp")]
public class Example19_5 
{
    public static void MakeFile() 
    {
        // Create a new file to work with
        FileStream fsOut = File.Create(@"c:\\temp\\test.txt");
        // Create a StreamWriter to handle writing
        StreamWriter sw = new StreamWriter(fsOut);
        // And write some data
        sw.WriteLine(""Twas brillig, and the slithy toves");
        sw.WriteLine("Did gyre and gimble in the wabe.");
        sw.Flush();
        sw.Close();
    }
}

Illustrates encrypting a file

/*
Mastering Visual C# .NET
by Jason Price, Mike Gunderloy
Publisher: Sybex;
ISBN: 0782129110
*/
/*
  Example19_9.cs illustrates encrypting a file
*/
using System;
using System.IO;
using System.Security.Cryptography;
public class Example19_9 
{
    public static void Main() 
    {
        // Create a new file to work with
        FileStream fsOut = File.Create(@"c:\temp\encrypted.txt");
        // Create a new crypto provider
        TripleDESCryptoServiceProvider tdes = 
            new TripleDESCryptoServiceProvider();
        // Create a cryptostream to encrypt to the filestream
        CryptoStream cs = new CryptoStream(fsOut, tdes.CreateEncryptor(), 
            CryptoStreamMode.Write);
        // Create a StreamWriter to format the output
        StreamWriter sw = new StreamWriter(cs);
        // And write some data
        sw.WriteLine(""Twas brillig, and the slithy toves");
        sw.WriteLine("Did gyre and gimble in the wabe.");
        sw.Flush();
        sw.Close();
        // save the key and IV for future use
        FileStream fsKeyOut = File.Create(@"c:\\temp\encrypted.key");
        
        // use a BinaryWriter to write formatted data to the file
        BinaryWriter bw = new BinaryWriter(fsKeyOut);
        // write data to the file
        bw.Write( tdes.Key );
        bw.Write( tdes.IV );
        // flush and close
        bw.Flush();
        bw.Close();
    }
}