在安全性要求比較高的系統中都會涉及到數據的加密、解密。.NET爲我們封裝了常用的加密算法，例如：MD5,DES,RSA等。有可逆加密，也有非可逆加密;有對稱加密，也有非對稱加密。加密、解密一般會用在軟件的註冊碼，系統密碼，通訊中。今天我就來分享，彙總一下C#.NET加密、解密的實現方法。
一、不可逆加密
不可逆加密一般不會涉及到解密。也就是是加密之後的密文不能還原成原來的明文。這種算法一般用於生成自信摘要，確保數據的完整性及防篡改。
使用FormsAuthentication類加密
using System.Web.Security;
namespace EncyptDemo
{
public class WebEncryptor
{
/// <summary>
/// SHA1加密字符串
/// </summary>
/// <param name="source">源字符串</param>
/// <returns>加密後的字符串</returns>
public string SHA1(string source)
{
return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "SHA1");
}
/// <summary>
/// MD5加密字符串
/// </summary>
/// <param name="source">源字符串</param>
/// <returns>加密後的字符串</returns>
public string MD5(string source)
{
return FormsAuthentication.HashPasswordForStoringInConfigFile(source, "MD5"); ;
}
}
}
使用MD5CryptoServiceProvider類生成MD5字符串
using System;
using System.Security.Cryptography;
using System.Text;
namespace EncyptDemo
{
public class MD5Helper
{
public string GetMD5_32(string s, string _input_charset = "utf8")
{
MD5 md5 = new MD5CryptoServiceProvider();
byte[] t = md5.ComputeHash(Encoding.GetEncoding(_input_charset).GetBytes(s));
StringBuilder sb = new StringBuilder(32);
for (int i = 0; i < t.Length; i++)
{
sb.Append(t[i].ToString("x").PadLeft(2, '0'));
}
return sb.ToString();
}
//16位加密
public static string GetMd5_16(string s)
{
MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();
string t2 = BitConverter.ToString(md5.ComputeHash(UTF8Encoding.Default.GetBytes(s)), 4, 8);
t2 = t2.Replace("-", "");
return t2;
}
}
}
二、可逆加密、解密
可逆加密，這種算法加密之後的密碼文可以解密成原來的明文。比如通訊的時候，數據的發送方和接收方約定好加密和解密的key，發送放把原始數據加密之後開始發送，接收放收到數據之後開始解密，把密文原來成明文。
可逆加密又分爲對稱加密和非對稱加密。所謂對稱加密就是加密和解密的算法一樣，也就是用來加密的key和解密的key是完全一樣的。而非對稱加密加密的key和解密的key是不一樣的，加密是用公鑰，解密是用私鑰。
2.1、對稱加密
對稱加密算法是應用較早的加密算法，技術成熟。在對稱加密算法中，數據發信方將明文（原始數據）和加密密鑰一起經過特殊加密算法處理後，使其變成複雜的加密密文發送出去。收信方收到密文後，若想解讀原文，則需要使用加密用過的密鑰及相同算法的逆算法對密文進行解密，才能使其恢復成可讀明文。
在對稱加密算法中，使用的密鑰只有一個，發收信雙方都使用這個密鑰對數據進行加密和解密，這就要求解密方事先必須知道加密密鑰。對稱加密算法的特點是算法公開、計算量小、加密速度快、加密效率高。不足之處是，交易雙方都使用同樣鑰匙，安全性得不到保證。此外，每對用戶每次使用對稱加密算法時，都需要使用其他人不知道的惟一鑰匙，這會使得發收信雙方所擁有的鑰匙數量成幾何級數增長，密鑰管理成爲用戶的負擔。對稱加密算法在分佈式網絡系統上使用較爲困難，主要是因爲密鑰管理困難，使用成本較高。在計算機專網系統中廣泛使用的對稱加密算法有DES、IDEA和AES。
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
namespace EncyptDemo
{
public class SymmetryEncrypt
{
private SymmetricAlgorithm mobjCryptoService;
private string Key;
/// <summary>
/// 對稱加密類的構造函數
/// </summary>
public SymmetryEncrypt()
{
mobjCryptoService = new RijndaelManaged();
Key = "Guz(%&hj7x89H$yuBI0456FtmaT5&fvHUFCy76*h%(HilJ$lhj!y6&(*jkP87jH7";
}
/// <summary>
/// 獲得密鑰
/// </summary>
/// <returns>密鑰</returns>
private byte[] GetLegalKey()
{
string sTemp = Key;
mobjCryptoService.GenerateKey();
byte[] bytTemp = mobjCryptoService.Key;
int KeyLength = bytTemp.Length;
if (sTemp.Length > KeyLength)
sTemp = sTemp.Substring(0, KeyLength);
else if (sTemp.Length < KeyLength)
sTemp = sTemp.PadRight(KeyLength, ' ');
return ASCIIEncoding.ASCII.GetBytes(sTemp);
}
/// <summary>
/// 獲得初始向量IV
/// </summary>
/// <returns>初試向量IV</returns>
private byte[] GetLegalIV()
{
string sTemp = "E4ghj*Ghg7!rNIfb&95GUY86GfghUb#er57HBh(u%g6HJ($jhWk7&!hg4ui%$hjk";
mobjCryptoService.GenerateIV();
byte[] bytTemp = mobjCryptoService.IV;
int IVLength = bytTemp.Length;
if (sTemp.Length > IVLength)
sTemp = sTemp.Substring(0, IVLength);
else if (sTemp.Length < IVLength)
sTemp = sTemp.PadRight(IVLength, ' ');
return ASCIIEncoding.ASCII.GetBytes(sTemp);
}
/// <summary>
/// 加密方法
/// </summary>
/// <param name="Source">待加密的串</param>
/// <returns>經過加密的串</returns>
public string Encrypto(string Source)
{
byte[] bytIn = UTF8Encoding.UTF8.GetBytes(Source);
MemoryStream ms = new MemoryStream();
mobjCryptoService.Key = GetLegalKey();
mobjCryptoService.IV = GetLegalIV();
ICryptoTransform encrypto = mobjCryptoService.CreateEncryptor();
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Write);
cs.Write(bytIn, 0, bytIn.Length);
cs.FlushFinalBlock();
ms.Close();
byte[] bytOut = ms.ToArray();
return Convert.ToBase64String(bytOut);
}
/// <summary>
/// 解密方法
/// </summary>
/// <param name="Source">待解密的串</param>
/// <returns>經過解密的串</returns>
public string Decrypto(string Source)
{
byte[] bytIn = Convert.FromBase64String(Source);
MemoryStream ms = new MemoryStream(bytIn, 0, bytIn.Length);
mobjCryptoService.Key = GetLegalKey();
mobjCryptoService.IV = GetLegalIV();
ICryptoTransform encrypto = mobjCryptoService.CreateDecryptor();
CryptoStream cs = new CryptoStream(ms, encrypto, CryptoStreamMode.Read);
StreamReader sr = new StreamReader(cs);
return sr.ReadToEnd();
}
}
}
在對稱加密算法中比較著名和常用的就是大名鼎鼎的DES加密算法，它安全性比較高的一種算法，目前只有一種方法可以破解該算法，那就是窮舉法。下面我們來看看.NET中要使用DES加密怎麼實現？
using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;
namespace EncyptDemo
{
public class DESHeper
{
//默認密鑰向量
private static byte[] Keys = { 0x12, 0x34, 0x56, 0x78, 0x90, 0xAB, 0xCD, 0xEF };
/// <summary>
/// DES加密字符串
/// </summary>
/// <param name="encryptString">待加密的字符串</param>
/// <param name="encryptKey">加密密鑰,要求爲8位</param>
/// <returns>加密成功返回加密後的字符串，失敗返回源串</returns>
public static string EncryptDES(string encryptString, string encryptKey)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(encryptKey.Substring(0, 8));
byte[] rgbIV = Keys;
byte[] inputByteArray = Encoding.UTF8.GetBytes(encryptString);
DESCryptoServiceProvider dCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream, dCSP.CreateEncryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
cStream.Write(inputByteArray, 0, inputByteArray.Length);
cStream.FlushFinalBlock();
return Convert.ToBase64String(mStream.ToArray());
}
catch
{
return encryptString;
}
}
/// <summary>
/// DES解密字符串
/// </summary>
/// <param name="decryptString">待解密的字符串</param>
/// <param name="decryptKey">解密密鑰,要求爲8位,和加密密鑰相同</param>
/// <returns>解密成功返回解密後的字符串，失敗返源串</returns>
public static string DecryptDES(string decryptString, string decryptKey)
{
try
{
byte[] rgbKey = Encoding.UTF8.GetBytes(decryptKey);
byte[] rgbIV = Keys;
byte[] inputByteArray = Convert.FromBase64String(decryptString);
DESCryptoServiceProvider DCSP = new DESCryptoServiceProvider();
MemoryStream mStream = new MemoryStream();
CryptoStream cStream = new CryptoStream(mStream, DCSP.CreateDecryptor(rgbKey, rgbIV), CryptoStreamMode.Write);
cStream.Write(inputByteArray, 0, inputByteArray.Length);
cStream.FlushFinalBlock();
return Encoding.UTF8.GetString(mStream.ToArray());
}
catch
{
return decryptString;
}
}
/// <summary>
/// DES加密方法
/// </summary>
/// <param name="strPlain">明文</param>
/// <param name="strDESKey">密鑰</param>
/// <param name="strDESIV">向量</param>
/// <returns>密文</returns>
public string DESEncrypt(string strPlain, string strDESKey, string strDESIV)
{
//把密鑰轉換成字節數組
byte[] bytesDESKey = ASCIIEncoding.ASCII.GetBytes(strDESKey);
//把向量轉換成字節數組
byte[] bytesDESIV = ASCIIEncoding.ASCII.GetBytes(strDESIV);
//聲明1個新的DES對象
DESCryptoServiceProvider desEncrypt = new DESCryptoServiceProvider();
//開闢一塊內存流
MemoryStream msEncrypt = new MemoryStream();
//把內存流對象包裝成加密流對象
CryptoStream csEncrypt = new CryptoStream(msEncrypt, desEncrypt.CreateEncryptor(bytesDESKey, bytesDESIV), CryptoStreamMode.Write);
//把加密流對象包裝成寫入流對象
StreamWriter swEncrypt = new StreamWriter(csEncrypt);
//寫入流對象寫入明文
swEncrypt.WriteLine(strPlain);
//寫入流關閉
swEncrypt.Close();
//加密流關閉
csEncrypt.Close();
//把內存流轉換成字節數組，內存流現在已經是密文了
byte[] bytesCipher = msEncrypt.ToArray();
//內存流關閉
msEncrypt.Close();
//把密文字節數組轉換爲字符串，並返回
return UnicodeEncoding.Unicode.GetString(bytesCipher);
}
/// <summary>
/// DES解密方法
/// </summary>
/// <param name="strCipher">密文</param>
/// <param name="strDESKey">密鑰</param>
/// <param name="strDESIV">向量</param>
/// <returns>明文</returns>
public string DESDecrypt(string strCipher, string strDESKey, string strDESIV)
{
//把密鑰轉換成字節數組
byte[] bytesDESKey = ASCIIEncoding.ASCII.GetBytes(strDESKey);
//把向量轉換成字節數組
byte[] bytesDESIV = ASCIIEncoding.ASCII.GetBytes(strDESIV);
//把密文轉換成字節數組
byte[] bytesCipher = UnicodeEncoding.Unicode.GetBytes(strCipher);
//聲明1個新的DES對象
DESCryptoServiceProvider desDecrypt = new DESCryptoServiceProvider();
//開闢一塊內存流，並存放密文字節數組
MemoryStream msDecrypt = new MemoryStream(bytesCipher);
//把內存流對象包裝成解密流對象
CryptoStream csDecrypt = new CryptoStream(msDecrypt, desDecrypt.CreateDecryptor(bytesDESKey, bytesDESIV), CryptoStreamMode.Read);
//把解密流對象包裝成讀出流對象
StreamReader srDecrypt = new StreamReader(csDecrypt);
//明文=讀出流的讀出內容
string strPlainText = srDecrypt.ReadLine();
//讀出流關閉
srDecrypt.Close();
//解密流關閉
csDecrypt.Close();
//內存流關閉
msDecrypt.Close();
//返回明文
return strPlainText;
}
}
}
除此之外我們還可以用DES加密文件：
using System;
using System.IO;
using System.Security.Cryptography;
namespace EncyptDemo
{
public class FileEncrypt
{
private static void EncryptData(String pathInput, String pathOutput, byte[] desKey, byte[] desIV)
{
//Create the file streams to handle the input and output files.
FileStream fin = new FileStream(pathInput, FileMode.Open, FileAccess.Read);
FileStream fout = new FileStream(pathOutput, FileMode.OpenOrCreate, FileAccess.Write);
fout.SetLength(0);
//Create variables to help with read and write.
byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
long rdlen = 0; //This is the total number of bytes written.
long totlen = fin.Length; //This is the total length of the input file.
int len; //This is the number of bytes to be written at a time.
DES des = new DESCryptoServiceProvider();
CryptoStream encStream = new CryptoStream(fout, des.CreateEncryptor(desKey, desIV), CryptoStreamMode.Write);
//Read from the input file, then encrypt and write to the output file.
while (rdlen < totlen)
{
len = fin.Read(bin, 0, 100);
encStream.Write(bin, 0, len);
rdlen = rdlen + len;
}
encStream.Close();
fout.Close();
fin.Close();
}
//解密文件
private static void DecryptData(String pathInput, String pathOutput, byte[] desKey, byte[] desIV)
{
//Create the file streams to handle the input and output files.
FileStream fin = new FileStream(pathInput, FileMode.Open, FileAccess.Read);
FileStream fout = new FileStream(pathOutput, FileMode.OpenOrCreate, FileAccess.Write);
fout.SetLength(0);
//Create variables to help with read and write.
byte[] bin = new byte[100]; //This is intermediate storage for the encryption.
long rdlen = 0; //This is the total number of bytes written.
long totlen = fin.Length; //This is the total length of the input file.
int len; //This is the number of bytes to be written at a time.
DES des = new DESCryptoServiceProvider();
CryptoStream encStream = new CryptoStream(fout, des.CreateDecryptor(desKey, desIV), CryptoStreamMode.Write);
//Read from the input file, then encrypt and write to the output file.
while (rdlen < totlen)
{
len = fin.Read(bin, 0, 100);
encStream.Write(bin, 0, len);
rdlen = rdlen + len;
}
encStream.Close();
fout.Close();
fin.Close();
}
}
}
2.2、非對稱加密
不對稱加密算法使用兩把完全不同但又是完全匹配的一對鑰匙—公鑰和私鑰。在使用不對稱加密算法加密文件時，只有使用匹配的一對公鑰和私鑰，才能完成對明文的加密和解密過程。加密明文時採用公鑰加密，解密密文時使用私鑰才能完成，而且發信方（加密者）知道收信方的公鑰，只有收信方（解密者）纔是唯一知道自己私鑰的人。不對稱加密算法的基本原理是，如果發信方想發送只有收信方纔能解讀的加密信息，發信方必須首先知道收信方的公鑰，然後利用收信方的公鑰來加密原文；收信方收到加密密文後，使用自己的私鑰才能解密密文。顯然，採用不對稱加密算法，收發信雙方在通信之前，收信方必須將自己早已隨機生成的公鑰送給發信方，而自己保留私鑰。由於不對稱算法擁有兩個密鑰，因而特別適用於分佈式系統中的數據加密。
廣泛應用的不對稱加密算法有RSA算法和美國國家標準局提出的DSA。以不對稱加密算法爲基礎的加密技術應用非常廣泛。尤其是在Linux系統下會經常用到這種非對稱加密。反正你只需要記住一點有公鑰和私鑰對的就是非對稱加密。
下面我們來看看C#中的怎麼實現RSA非對稱加密。
首先，我們要生成一個公鑰和私鑰對。
using System.IO;
using System.Security.Cryptography;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
using (StreamWriter writer = new StreamWriter("PrivateKey.xml",false)) //這個文件要保密...
{
writer.WriteLine(rsa.ToXmlString(true));
}
using (StreamWriter writer = new StreamWriter("PublicKey.xml",false))
{
writer.WriteLine(rsa.ToXmlString(false));
}
}
}
}
運行上面的控制檯程序會在程序目錄下生成配對的公鑰和私鑰文件。
接下來寫一個RSA加密解密類
using System;
using System.Collections.Generic;
using System.linq;
using System.Text;
using System.Security.Cryptography;
namespace ClassLibrary1
{
public class RSAHelper
{
static string PublicKey = @"<RSAKeyValue><Modulus>nwbjN1znmyL2KyOIrRy/PbWZpTi+oekJIoGNc6jHCl0JNZLFHNs70fyf7y44BH8L8MBkSm5sSwCZfLm5nAsDNOmuEV5Uab5DuWYSE4R2Z3NkKexJJ4bnmXEZYXPMzTbXIpyvU2y9YVrz1BjjRPeHsb6daVdrBgjs4+2b/ok9myM=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>";
static string PrivateKey = @"<RSAKeyValue><Modulus>nwbjN1znmyL2KyOIrRy/PbWZpTi+oekJIoGNc6jHCl0JNZLFHNs70fyf7y44BH8L8MBkSm5sSwCZfLm5nAsDNOmuEV5Uab5DuWYSE4R2Z3NkKexJJ4bnmXEZYXPMzTbXIpyvU2y9YVrz1BjjRPeHsb6daVdrBgjs4+2b/ok9myM=</Modulus><Exponent>AQAB</Exponent><P>2PfagXD2zKzUGLkAXpC+04u0xvESpO1PbTUOGA2m8auviEMNz8VempJ/reOlJjEO2q2nrUsbtqKd0m96Cxz0Fw==</P><Q>u6Kiit1XhIgRD9jQnQh36y28LOmku2Gqn9KownMSVGhWzkkHQPw77A2h1OirQiKe6aOIO/yxdwTI/9Ds4Kwc1Q==</Q><DP>GfwtPj1yQXcde8yEX88EG7/qqbzrl7cYQSMOihDwgpcmUbJ+L/kaaHbNNd1CxT0w4z3TDC0np4r4TeCuBDC2hw==</DP><DQ>hl8I0jOC2klrFpMpilunLUeaa/uCWiKuQzhkXKR1qvbxu1b3F+XKr9hvXX6mLn2GmkDfbj4fhOFrZC/lg1weZQ==</DQ><InverseQ>P1y+6el2+1LsdwL14hYCILvsTKGokGSKD35N7HakLmHNjXiU05hN1cnXMsGIZGg+pNHmz/yuPmgNLJoNZCQiCg==</InverseQ><D>D27DriO99jg2W4lfQi2AAaUV/Aq9tUjAMjEQYSEH7+GHe0N7DYnZDE/P1Y5OsWEC76I8GV0N9Vlhi9EaSiJndRvUgphTL2YuAjrVr59Il+lwh/LUBN46AX3cmQm3cFf1F1FXKj4S+QCx/qrCH4mmKpynuQsPL/1XiQSWpugI30E=</D></RSAKeyValue>";
static RSACryptoServiceProvider rsaProvider = new RSACryptoServiceProvider(1024);
public static byte[] EncryptData(byte[] data)
{
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(1024);
//將公鑰導入到RSA對象中，準備加密；
rsa.FromXmlString(PublicKey);
//對數據data進行加密，並返回加密結果；
//第二個參數用來選擇Padding的格式
byte[] buffer = rsa.Encrypt(data, false);
return buffer;
}
public static byte[] DecryptData(byte[] data)
{
RSACryptoServiceProvider rsa = new RSACryptoServiceProvider(1024);
//將私鑰導入RSA中，準備解密；
rsa.FromXmlString(PrivateKey);
//對數據進行解密，並返回解密結果；
return rsa.Decrypt(data, false);
}
}
}
上面的PublicKey和PrivateKey非別是文件PublicKey.xml和PrivateKey.xml裏面的內容。測試這個RSAHelper的方法：
[TestMethod()]
public void DecryptDataTest()
{
byte[] data = System.Text.ASCIIEncoding.ASCII.GetBytes("Hello");
byte[] data2 = RSAHelper.EncryptData(data);
byte[] actual;
actual = RSAHelper.DecryptData(data2);
var a = System.Text.ASCIIEncoding.ASCII.GetString(actual);
Assert.AreEqual("Hello", a);
}
可以看到上面通過EncryptData加密的數據能夠通過DecryptData解密成原來的明文（Hello），而這個加密和解密用是不同的密鑰。