Csharp/CSharp Tutorial/Security/Encryption

PublicKey Cryptography

<source lang="csharp">using System; using System.Security.Cryptography;

 class Class1
 {
   static void Main(string[] args)
   {
     string dataToSign = "this is a test.";
     byte[] data_Bytes = System.Text.Encoding.ASCII.GetBytes( dataToSign );
     
     SHA1Managed sha1 = new SHA1Managed();
     byte[] hash_Bytes = sha1.ruputeHash( data_Bytes );
   
     DSACryptoServiceProvider dsa = new DSACryptoServiceProvider(); 
     DSASignatureFormatter sigFormatter = new DSASignatureFormatter(dsa);
     sigFormatter.SetHashAlgorithm("SHA1");
     byte[] signedHash = sigFormatter.CreateSignature( hash_Bytes );
     byte[] remote_SignedHash = signedHash;
     byte[] remote_HashedValue = hash_Bytes;
     DSASignatureDeformatter sigDeformatter = new DSASignatureDeformatter( dsa );
     sigDeformatter.SetHashAlgorithm( "SHA1" );
     Console.WriteLine(sigDeformatter.VerifySignature( remote_HashedValue, remote_SignedHash ));
     RSACryptoServiceProvider rsa=  new RSACryptoServiceProvider();
     byte[] dataToEncrypt = System.Text.Encoding.Unicode.GetBytes( "Encrypt THIS!" );
     byte[] encrypted_Bytes;
     byte[] decrypted_Bytes;
     encrypted_Bytes = rsa.Encrypt( dataToEncrypt, false );
     Console.WriteLine("RSA-encrypted data is {0} bytes long.", encrypted_Bytes.Length);
     decrypted_Bytes = rsa.Decrypt( encrypted_Bytes, false );
     Console.WriteLine("RSA-decrypted string is {0}.", System.Text.Encoding.Unicode.GetString( decrypted_Bytes ));
   }
 }</source>

Secret Key Cryptography: RijndaelManaged

<source lang="csharp">using System; using System.IO; using System.Text; using System.Security.Cryptography;

 class Class1
 {
   static void Main(string[] args)
   {
     byte[] bin = new byte[100]; // 100 byte buffer
     FileStream fsIn = new FileStream("input.txt", FileMode.Open, FileAccess.Read);
     long rdLen = 0;
     long totLen = fsIn.Length;
     int len;
     RijndaelManaged rm = new RijndaelManaged();
     rm.GenerateIV();
     rm.GenerateKey();
     FileStream fsOut_RM = new FileStream("outputRM.txt", FileMode.Create, FileAccess.Write);
     CryptoStream rmStream = new CryptoStream( fsOut_RM,
       rm.CreateEncryptor(), CryptoStreamMode.Write);
     while ( rdLen < totLen )
     {
       len = fsIn.Read(bin, 0, 100);
       System.Diagnostics.Debug.WriteLine("Read " + len.ToString() + " bytes.");
       rmStream.Write(bin, 0, len );
       rdLen += len;
       Console.WriteLine("{0} Bytes Read.", rdLen );
     }
     fsIn.Close();
   }
 }</source>

Symmetric Encryption

<source lang="csharp">using System; using System.IO; using System.Security; using System.Security.Cryptography; using System.Collections.Generic; using System.Text;

   class Program
   {
       static void Main(string[] args)
       {
           RijndaelManaged rmCrypto = new RijndaelManaged();
           byte[] key = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,0x09, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16 };
           byte[] IV = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16 };
           string clearMessage = "this is a test";
           FileStream fs = new FileStream("encrypted.dat", FileMode.Create);
           CryptoStream cs = new CryptoStream(fs, rmCrypto.CreateEncryptor(key, IV), CryptoStreamMode.Write);
           cs.Write(System.Text.ASCIIEncoding.ASCII.GetBytes(clearMessage),0, clearMessage.Length);
           cs.Close();
           fs.Close();
           FileStream fs2 = new FileStream("encrypted.dat", FileMode.Open);
           CryptoStream cs2 = new CryptoStream(fs2, rmCrypto.CreateDecryptor(key, IV), CryptoStreamMode.Read);
           byte[] decryptedData = new byte[fs2.Length];
           cs2.Read(decryptedData, 0, (int)fs2.Length);
           cs2.Close();
           fs2.Close();
           Console.WriteLine(System.Text.ASCIIEncoding.ASCII.GetString(decryptedData));
       }
   }</source>