asymmetricexample.cs

在C#中实现加密解密

using System;
using System.Security.Cryptography;
using System.IO;
using System.Xml;

namespace CryptographyExamplesInCS
{
	/// <summary>
	/// Summary description for AsymmetricExample.
	/// </summary>
	public class AsymmetricExample
	{
		private string keyfilename = "c:\\AsymmetricKey.xml";
		private string filename = "c:\\AsymmetricExample.xml";
		private RSACryptoServiceProvider cryptoprovider = new RSACryptoServiceProvider(2048);
		
		public string Server = "(local)";
		public string Database = "Northwind";
		public string User = "sa";
		public string Password = "";
		public string Provider = "SQLOLEDB";

		public AsymmetricExample()
		{
			if(!System.IO.File.Exists(keyfilename))
			{
				FileStream filewriter = new FileStream(keyfilename, FileMode.Create);
				XmlTextWriter xmlwriter = new XmlTextWriter(filewriter, System.Text.Encoding.UTF8);
				
				xmlwriter.WriteRaw(cryptoprovider.ToXmlString(true));
				xmlwriter.Close();
				filewriter.Close();
			}
			else
			{
				FileStream filereader = new FileStream(keyfilename, FileMode.Open);
				XmlTextReader xmlreader = new XmlTextReader(filereader);
				XmlDocument xmldoc = new XmlDocument();
				
				xmldoc.Load(xmlreader);

				cryptoprovider.FromXmlString(xmldoc.InnerXml);
			}
		}

		public void Encrypt()
		{
			StringWriter memwriter = new StringWriter();
			XmlTextWriter xmlwriter = new XmlTextWriter(memwriter);

			xmlwriter.WriteStartDocument();
			xmlwriter.WriteStartElement("Configuration");
			xmlwriter.WriteStartElement("Data");
			xmlwriter.WriteElementString("Server", Server);
			xmlwriter.WriteElementString("Database", Database);
			xmlwriter.WriteElementString("User", User);
			xmlwriter.WriteElementString("Password", Password);
			xmlwriter.WriteElementString("Provider", Provider);
			xmlwriter.WriteEndElement();
			xmlwriter.WriteEndElement();
			xmlwriter.WriteEndDocument();
			
			FileStream cryptowriter = new FileStream(filename, FileMode.Create);
			
			string contents = memwriter.ToString();
			byte[] xml = new byte[contents.Length];

			for(int n=0;n<contents.Length;n++)
			{
				xml[n] = Convert.ToByte(contents[n]);
			}
			
			byte[] text = cryptoprovider.Encrypt(xml, false);
			
			cryptowriter.Write(text, 0, text.Length);
			cryptowriter.Close();
			xmlwriter.Close();
			memwriter.Close();
		}
		
		public void Decrypt()
		{
			if(!File.Exists(filename))
				this.Encrypt();

			FileStream filereader = new FileStream(filename, FileMode.Open);

			byte[] contents = new byte[filereader.Length];

			filereader.Read(contents, 0, System.Convert.ToInt32(filereader.Length));

			byte[] xml = cryptoprovider.Decrypt(contents, false);
			
			char[] text = new char[xml.Length];

			xml.CopyTo(text, 0);
			
			string stringtext = new string(text);

			StringReader memreader = new StringReader(stringtext);
			XmlTextReader xmlreader = new XmlTextReader(memreader);
			XmlDocument xmldoc = new XmlDocument();

			xmldoc.Load(xmlreader);

			string xpath = "/Configuration/Data/";

			Server = xmldoc.SelectSingleNode(xpath + "Server").InnerText;
			Database = xmldoc.SelectSingleNode(xpath + "Database").InnerText;
			User = xmldoc.SelectSingleNode(xpath + "User").InnerText;
			Password = xmldoc.SelectSingleNode(xpath + "Password").InnerText;
			Provider = xmldoc.SelectSingleNode(xpath + "Provider").InnerText;

			filereader.Close();
			memreader.Close();
			xmlreader.Close();
		}
	}
}