大家好，我是阿赵。
这里分享个C#对称加密字符串的方法。
所谓的对称加密，意思是把原字符串通过秘钥，加密成另外一串字符串，然后可以通过秘钥还原回原字符串。
这种方法是基于Base64的，加密方法如下：
/// <summary>/// 加密字符串/// </summary>/// <param name="str">需要加密的字符串</param>/// <param name="encryptKey">加密key，长度4</param>/// <returns></returns>static public string Encrypt(string str, string encryptKey){if(string.IsNullOrEmpty(str)){return str;}encryptKey = CheckEncryptKeyString(encryptKey,4);DESCryptoServiceProvider descsp = new DESCryptoServiceProvider(); //实例化加/解密类对象 byte[] key = Encoding.Unicode.GetBytes(encryptKey); //定义字节数组，用来存储密钥 byte[] data = Encoding.Unicode.GetBytes(str);//定义字节数组，用来存储要加密的字符串 MemoryStream MStream = new MemoryStream(); //实例化内存流对象 //使用内存流实例化加密流对象 CryptoStream CStream = new CryptoStream(MStream, descsp.CreateEncryptor(key, key), CryptoStreamMode.Write);CStream.Write(data, 0, data.Length); //向加密流中写入数据 CStream.FlushFinalBlock(); //释放加密流 return Convert.ToBase64String(MStream.ToArray());//返回加密后的字符串 }
这个方法支持加密key长度为4，如果长度不是4将会报错，所以这里加了一个检查key长度的方法，传入的长度是4，如果不够4，则补空格，如果超过4，则只取4个字符：
static public string CheckEncryptKeyString(string str,int len){if(str.Length == len){return str;}if(str.Length>len){return str.Substring(0, len);}else{string newstr = str + new string(' ', len - str.Length);return newstr;}}
下面是解密的方法：
/// <summary> /// 解密字符串 /// </summary> /// <param name="str">要解密的字符串</param> /// <returns>解密后的字符串</returns> static public string Decrypt(string str, string encryptKey){if (string.IsNullOrEmpty(str)){return str;}encryptKey = CheckEncryptKeyString(encryptKey,4);DESCryptoServiceProvider descsp = new DESCryptoServiceProvider(); //实例化加/解密类对象 byte[] key = Encoding.Unicode.GetBytes(encryptKey); //定义字节数组，用来存储密钥 byte[] data = Convert.FromBase64String(str);//定义字节数组，用来存储要解密的字符串 MemoryStream MStream = new MemoryStream(); //实例化内存流对象 //使用内存流实例化解密流对象 CryptoStream CStream = new CryptoStream(MStream, descsp.CreateDecryptor(key, key), CryptoStreamMode.Write);CStream.Write(data, 0, data.Length); //向解密流中写入数据 CStream.FlushFinalBlock(); //释放解密流 return Encoding.Unicode.GetString(MStream.ToArray()); //返回解密后的字符串 }
第二种方法是在第一种方法的基础上做了一些修改，可以支持8位长度的秘钥：
/// <summary>
/// DES加密字符串
/// </summary>
/// <param name="encryptString">待加密的字符串</param>
/// <param name="encryptKey">加密密钥,要求为8位</param>
/// <returns>加密成功返回加密后的字符串，失败返回null</returns>
public static string EncryptDES(string encryptString, string encryptKey)
{try{encryptKey = CheckEncryptKeyString(encryptKey, 8);byte[] rgbKey = ASCIIEncoding.ASCII.GetBytes(encryptKey);byte[] rgbIV = rgbKey;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();StringBuilder ret = new StringBuilder();foreach (byte b in mStream.ToArray()){ret.AppendFormat("{0:X2}", b);}ret.ToString();return ret.ToString();}catch{return null;}
}
由于秘钥长度一定要是8位，不然会报错，所以还是继续用刚才判断的方法CheckEncryptKeyString，这次传入长度8。
下面是解密方法：
/// <summary>
/// DES解密字符串
/// </summary>
/// <param name="decryptString">待解密的字符串</param>
/// <param name="decryptKey">解密密钥,要求为8位,和加密密钥相同</param>
/// <returns>解密成功返回解密后的字符串，失败返回null</returns>
public static string DecryptDES(string decryptString, string decryptKey)
{try{decryptKey = CheckEncryptKeyString(decryptKey, 8);byte[] rgbKey = ASCIIEncoding.ASCII.GetBytes(decryptKey);byte[] rgbIV = rgbKey;byte[] inputByteArray = new byte[decryptString.Length / 2];for (int x = 0; x < decryptString.Length / 2; x++){int i = (Convert.ToInt32(decryptString.Substring(x * 2, 2), 16));inputByteArray[x] = (byte)i;}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(Exception ex){return null;}
}
