/* основные классы */

public class MD5HashHelper 
{ 

	public byte[] GetHash(string message) 
	{ 
		byte[] data; 
		data = UTF8Encoding.ASCII.GetBytes(message); 
		MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); 
		return md5.ComputeHash(data, 0, data.Length); 
	} 

	public bool VerifyHash(string message, byte[] hash) 
	{ 
		byte[] data; 
		data = UTF8Encoding.ASCII.GetBytes(message); 
		MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); 
		byte[] hashTemp = md5.ComputeHash(data, 0, data.Length); 

		for (Int32 counter = 0; counter <= hash.Length - 1; counter += 1) 
		{
			if (hash[counter] != hashTemp[counter]) 
			{ 
				return false; 
			} 
		} 
		return true; 
	} 
}

public class DigitalSignatureHelper 
{ 
	private RSAParameters m_public; 

	public byte[] CreateSignature(byte[] hash) 
	{ 
		RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(); 
		RSAPKCS1SignatureFormatter RSAFormatter = new RSAPKCS1SignatureFormatter(RSA); 
		RSAFormatter.SetHashAlgorithm("MD5"); 
		m_public = RSA.ExportParameters(false); 
		return RSAFormatter.CreateSignature(hash); 
	} 

	public bool VerifySignature(byte[] hash, byte[] signedhash) 
	{ 
		RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(); 
		RSAParameters RSAKeyInfo = new RSAParameters(); 
		RSAKeyInfo.Modulus = m_public.Modulus; 
		RSAKeyInfo.Exponent = m_public.Exponent; 
		RSA.ImportParameters(RSAKeyInfo); 
		RSAPKCS1SignatureDeformatter RSADeformatter = new RSAPKCS1SignatureDeformatter(RSA); 
		RSADeformatter.SetHashAlgorithm("MD5"); 
		return RSADeformatter.VerifySignature(hash, signedhash); 
	} 
}

// *****************************************************************

/* использование */
public class Form1 : System.Windows.Forms.Form
{
		internal System.Windows.Forms.Button Button2;
		internal System.Windows.Forms.Button Button1;
		private System.Windows.Forms.TextBox textBox1;
		private System.Windows.Forms.TextBox textBox2;
		private System.Windows.Forms.Label label1;
		private System.Windows.Forms.Label label2;
		/// <summary>
		/// Required designer variable.
		/// </summary>
		private System.ComponentModel.Container components = null;

		public Form1()
		{
			//
			// Required for Windows Form Designer support
			//
			InitializeComponent();

			//
			// TODO: Add any constructor code after InitializeComponent call
			//
		}

		/// <summary>
		/// Clean up any resources being used.
		/// </summary>
		protected override void Dispose( bool disposing )
		{
			if( disposing )
			{
				if (components != null) 
				{
					components.Dispose();
				}
			}
			base.Dispose( disposing );
		}

		#region Windows Form Designer generated code
		/// <summary>
		/// Required method for Designer support - do not modify
		/// the contents of this method with the code editor.
		/// </summary>
		private void InitializeComponent()
		{
			this.Button2 = new System.Windows.Forms.Button();
			this.Button1 = new System.Windows.Forms.Button();
			this.textBox1 = new System.Windows.Forms.TextBox();
			this.textBox2 = new System.Windows.Forms.TextBox();
			this.label1 = new System.Windows.Forms.Label();
			this.label2 = new System.Windows.Forms.Label();
			this.SuspendLayout();
			// 
			// Button2
			// 
			this.Button2.Location = new System.Drawing.Point(224, 24);
			this.Button2.Name = "Button2";
			this.Button2.Size = new System.Drawing.Size(112, 23);
			this.Button2.TabIndex = 5;
			this.Button2.Text = "Generate Signature";
			this.Button2.Click += new System.EventHandler(this.Button2_Click);
			// 
			// Button1
			// 
			this.Button1.Location = new System.Drawing.Point(224, 64);
			this.Button1.Name = "Button1";
			this.Button1.Size = new System.Drawing.Size(112, 23);
			this.Button1.TabIndex = 4;
			this.Button1.Text = "Verify Signature";
			this.Button1.Click += new System.EventHandler(this.Button1_Click);
			// 
			// textBox1
			// 
			this.textBox1.Location = new System.Drawing.Point(120, 24);
			this.textBox1.Name = "textBox1";
			this.textBox1.Size = new System.Drawing.Size(96, 20);
			this.textBox1.TabIndex = 6;
			this.textBox1.Text = "My Signature";
			// 
			// textBox2
			// 
			this.textBox2.Location = new System.Drawing.Point(120, 64);
			this.textBox2.Name = "textBox2";
			this.textBox2.Size = new System.Drawing.Size(96, 20);
			this.textBox2.TabIndex = 7;
			this.textBox2.Text = "My Signature";
			// 
			// label1
			// 
			this.label1.Font = new System.Drawing.Font("Microsoft Sans Serif", 8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(178)));
			this.label1.Location = new System.Drawing.Point(8, 24);
			this.label1.Name = "label1";
			this.label1.TabIndex = 8;
			this.label1.Text = "Set Signature";
			// 
			// label2
			// 
			this.label2.Font = new System.Drawing.Font("Microsoft Sans Serif", 8.25F, System.Drawing.FontStyle.Bold, System.Drawing.GraphicsUnit.Point, ((System.Byte)(178)));
			this.label2.Location = new System.Drawing.Point(8, 64);
			this.label2.Name = "label2";
			this.label2.TabIndex = 9;
			this.label2.Text = "Verify Signature";
			// 
			// Form1
			// 
			this.AutoScaleBaseSize = new System.Drawing.Size(5, 13);
			this.ClientSize = new System.Drawing.Size(344, 110);
			this.Controls.Add(this.label2);
			this.Controls.Add(this.label1);
			this.Controls.Add(this.textBox2);
			this.Controls.Add(this.textBox1);
			this.Controls.Add(this.Button2);
			this.Controls.Add(this.Button1);
			this.MaximizeBox = false;
			this.Name = "Form1";
			this.StartPosition = System.Windows.Forms.FormStartPosition.CenterScreen;
			this.Text = "Digital Signature - By Fadi Abdel-qader";
			this.ResumeLayout(false);

		}
		#endregion

		/// <summary>
		/// The main entry point for the application.
		/// </summary>
		[STAThread]
		static void Main() 
		{
			Application.Run(new Form1());
		}

		DigitalSignatureHelper ds = new DigitalSignatureHelper(); 
		byte[] hash1; 
		byte[] hash2; 
		byte[] signedhash;

		private void Button2_Click(object sender, System.EventArgs e)
		{
			try //создание подписи
			{
				MD5HashHelper md5 = new MD5HashHelper(); 
				hash1 = md5.GetHash(textBox1.Text); 
				signedhash = ds.CreateSignature(hash1); 
				MessageBox.Show("Подпись успешно создана!");
			}
			catch(Exception ex){MessageBox.Show(ex.Message);}
			}

		private void Button1_Click(object sender, System.EventArgs e)
		{
			try//проверка подписи
			{
				MD5HashHelper md5 = new MD5HashHelper();
				hash2 = md5.GetHash(textBox2.Text); 

				if (ds.VerifySignature(hash2, signedhash)) 
				{ 
					MessageBox.Show("Ура! Подпись правильная!"); 
				} 
				else 
				{ 
					MessageBox.Show("Ой! Подпись неверная!"); 
				}
			}
			catch(Exception ex){MessageBox.Show(ex.Message);}
		}
}