public class Cryptography
{
  public static RSACryptoServiceProvider rsa;

  public static void AssignParameter()
  {
	const int PROVIDER_RSA_FULL = 1; 
	const string CONTAINER_NAME = "SpiderContainer";
	CspParameters cspParams;
	cspParams = new CspParameters(PROVIDER_RSA_FULL);
	cspParams.KeyContainerName = CONTAINER_NAME;
	cspParams.Flags = CspProviderFlags.UseMachineKeyStore;
	cspParams.ProviderName = "Microsoft Strong Cryptographic Provider";
	rsa = new RSACryptoServiceProvider(cspParams); 
  }

  public static string EncryptData(string data2Encrypt)
  {
	AssignParameter();
      StreamReader reader = new   StreamReader(@"C:\Inetpub\wwwroot\dotnetspiderencryption\publickey.xml");
	string publicOnlyKeyXML = reader.ReadToEnd();
	rsa.FromXmlString(publicOnlyKeyXML);
	reader.Close();

	//read plaintext, encrypt it to ciphertext

	byte[] plainbytes =	System.Text.Encoding.UTF8.GetBytes(data2Encrypt);
	byte[] cipherbytes = rsa.Encrypt(plainbytes,false);
	return Convert.ToBase64String(cipherbytes);
  }

  public static void AssignNewKey()
  {
	AssignParameter();
	
	//provide public and private RSA params
	StreamWriter writer = new   StreamWriter(@"C:\Inetpub\wwwroot\dotnetspiderencryption\privatekey.xml");
	string publicPrivateKeyXML = rsa.ToXmlString(true);
	writer.Write(publicPrivateKeyXML);
	writer.Close();

	//provide public only RSA params
	writer = new StreamWriter(@"C:\Inetpub\wwwroot\dotnetspiderencryption\publickey.xml");
	string publicOnlyKeyXML = rsa.ToXmlString(false);
	writer.Write(publicOnlyKeyXML);
	writer.Close();

  }

  public static string DecryptData(string data2Decrypt)
  {
	AssignParameter();

	byte[] getpassword = Convert.FromBase64String(data2Decrypt);
			
	StreamReader reader = new StreamReader(@"C:\Inetpub\wwwroot\dotnetspiderencryption\privatekey.xml");
	string publicPrivateKeyXML = reader.ReadToEnd();
	rsa.FromXmlString(publicPrivateKeyXML);
	reader.Close();
			
	//read ciphertext, decrypt it to plaintext
	byte[] plain =	rsa.Decrypt(getpassword,false); 
	return System.Text.Encoding.UTF8.GetString(plain);

}
}

Cryptography.AssignNewKey();

txt2.Text = Cryptography.EncryptData(txt1.Text);

Txt3.Text = Cryptography.DecryptData(txt2.Text);