Csharp/C Sharp/File Stream/File Cryptography

Illustrates asymmetric cryptography

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

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/*

 Example19_11.cs illustrates asymmetric cryptography

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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();
   }

}

      </source>

Illustrates declarative role-based security

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

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/*

 Example19_8.cs illustrates declarative role-based security

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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();
   }

}

      </source>

Illustrates decrypting a file

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

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/*

 Example19_10.cs illustrates decrypting a file

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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();
   }

}

      </source>

Illustrates demanding permissions

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

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/*

 Example19_5.cs illustrates demanding permissions

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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();
   }

}

      </source>

Illustrates encrypting a file

<source lang="csharp"> /* Mastering Visual C# .NET by Jason Price, Mike Gunderloy Publisher: Sybex; ISBN: 0782129110

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/*

 Example19_9.cs illustrates encrypting a file

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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();
   }

}

      </source>